U.S. patent number 3,772,668 [Application Number 05/213,703] was granted by the patent office on 1973-11-13 for freight security system.
This patent grant is currently assigned to Lectrolarm Custom Systems, Inc.. Invention is credited to William Van Smith.
United States Patent |
3,772,668 |
Smith |
November 13, 1973 |
FREIGHT SECURITY SYSTEM
Abstract
An electronic security system for safe-guarding freight against
theft while in transit and/or while sitting at a dock site. The
concept of the system is to plant a unique transceiver in the
freight package which responds with a coded signal when properly
interrogated, i. e., with a coded radio frequency. The system
includes a second transceiver, which is monitored by security
personnel, and which is positioned at a strategic location. The
monitored transceiver may be automatically triggered each time a
conveyance means, e. g., a truck or the like, passes a particular
point or it may be triggered manually. Triggering the monitored
transceiver causes the transmitted carrier frequency to be
modulated with a first coded audio signal. The planted transceiver
responds with a second coded signal, if the first signal was of the
proper frequency. The monitored transceiver includes a plurality of
decoding networks and a plurality of neon lights which respectively
respond to signals accepted by the decoding networks. Each light
and associated decoding network monitors a separate freight package
for purposes of alerting the security personnel when unauthorized
movement of the freight package is occurring. The system has the
capability of simultaneously safe-guarding numerous packages, e.
g., 50 or more, positioned at one location. Additionally, the
system is capable of discriminating or pinpointing the particular
conveyance means that is carrying the freight package.
Inventors: |
Smith; William Van (Memphis,
TN) |
Assignee: |
Lectrolarm Custom Systems, Inc.
(Memphis, TN)
|
Family
ID: |
22796170 |
Appl.
No.: |
05/213,703 |
Filed: |
December 29, 1971 |
Current U.S.
Class: |
340/8.1; 340/530;
342/42; 340/10.1; 340/539.1 |
Current CPC
Class: |
G08B
13/2431 (20130101); G08B 13/2417 (20130101); G01S
13/78 (20130101); G08B 13/2462 (20130101) |
Current International
Class: |
G08B
13/24 (20060101); G01S 13/00 (20060101); G01S
13/78 (20060101); G01s 001/02 () |
Field of
Search: |
;340/152T,38R,38L,224,309.1,152T,171PF ;343/6.5SS ;325/8 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Trafton; David L.
Claims
I claim:
1. An electronic freight security system comprising means
positioned at a first location for receiving radio frequency
signals, means positioned at said first location for transmitting
radio frequency signals, encoder means positioned at said first
location for modulating said transmitting means with a first narrow
band width predetermined fixed signal, means positioned at said
first location for simultaneously triggering said transmitting and
said encoder means, means positioned at a location remote from said
first location for receiving radio frequency signals, means
positioned at said remote location for transmitting radio signals,
decoder means positioned at said remote location for responding to
said first signal and for passing a narrow width of predetermined
frequencies, means positioned at said remote location for
amplifying said passed frequencies, encoder means positioned at
said remote location for modulating said transmitting means at said
remote location with a second narrow band width predetermined fixed
signal having a frequency different from said first signal, means
positioned at said remote location for discriminatively triggering
simultaneously said transmitting means and said encoder means thus
causing said remote transmitting means to operate only when said
decoder means responds to a signal transmitted from said first
location, decoder means positioned at said first location for
passing a signal having a narrow width of predetermined
frequencies, means positioned at said first location for amplifying
the signal passed by said adjacent decoder means, indicator means
positioned at said first location, and means positioned at said
first location for causing said indicator means to be energized
when said decoder means adjacent thereto responds to a signal
transmitted from said remote location; said triggering means
positioned at said first location includes activating means, a
first relay responsive to said activating means, a resistor, a
capacitor, said capacitor being charged when said first relay
responds to said activating means and discharges through said
resistor, a second relay for simultaneously energizing said
encoding means and said transmitting means, and means for coupling
said capacitor to said second relay to enable said second relay to
be energized by the charge on said capacitor for a predetermined
period of time as the charge on said capacitor discharges through
said resistor.
2. The system of claim 1 in which said activating means includes a
bellows actuated switching means, and an elongated resilient
tubular member containing a captured quantity of fluid which is
communicated with said switching means for displacing said bellows
thereof when said resilient member is squeezably compressed so as
to close said switching means.
3. An electronic freight security system for remotely monitoring
the physical location of a plurality of freight packages while in
transit or while at a dock site comprising means positioned at a
first location for receiving radio frequency signals, means
positioned at said first location for transmitting radio frequency
signals, encoding means positioned at said frist location for
modulating said transmitting means with a first narrow band width
predetermined fixed audio signal, means positioned at said first
location for simultaneously triggering said transmitting means and
said encoder means, means positioned in a plurality of packages at
a plurality of locations which are remote from said first location
for receiving radio frequency signals, means positioned in each of
said packages for transmitting radio signals, decoder means
positioned in each of said packages for respectively responding to
said first signal and for passing a narrow width of predetermined
frequencies, means positioned in each of said packages for
respectively amplifying said passed frequencies, encoder means
positioned in each of said packages for respectively modulating
said transmitting means with a plurality of audio signals of
predetermined unique frequencies, means positioned in said packages
for respectively triggering said transmitting means and said
encoder means thus causing said corresponding transmitting means of
said packages to operate only when said decoder means thereof
individually responds to a signal transmitted from said first
location, a plurality of decoder means positioned at said first
location for respectively accepting a plurality of audio signals of
predetermined unique frequencies, means positioned at said first
location for respectively amplifying the signals passed by said
adjacent corresponding decoder means, a plurality of indicator
means positioned at said first location, and a plurality of means
positioned at said first location for respectively causing said
indicator means to be energized when said corresponding decoding
means responds to a signal transmitted from said plurality of
transmitting means in said packages; said triggering means
positioned at said first location includes activating means, a
first relay responsive to said activating means, a resistor, a
capacitor, said capacitor being charged when said first relay
responds to said activating means and discharges through said
resistor, a second relay for simultaneously energizing said
encoding means and said transmitting means, and means for coupling
said capacitor to said second relay to enable said second relay to
be energized by the charge on said capacitor for a predetermined
period of time as the charge on said capacitor discharges through
said resistor.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to two-way electronic communications systems
for use with security systems, particularly safe-guarding freight
against theft while in transit.
A problem of increasing magnitude prevails in the field of
transportation wherein certain packages of freight are stolen from
the dock site, or the like, particularly high value items. The
problem has many facets, e.g., frieght handlers having unscrupulous
characters colluding with truck drives of bona fide agencies having
legitimate business at the dock site place the high-valued
commodity onto the truck where it may be transported to an assembly
point for receiving the stolen property. The obvious solution to
the above-mentioned problem is to simply place an armed guard with
the package so that it may be under constant surveillance by
security personnel. This solution is costly in manhours.
Additionally, a cunningly planned scheme could Conceivably involve
nullifying the guard's effectiveness by inducing bodily harm or the
like. However, the usual practice is for the unscrupulous personnel
to concentrate their efforts on the packages which are not under
surveillance.
SUMMARY OF THE INVENTION
The present invention is directed towards overcoming the
abovementioned problem. Solving the problem would be greatly
simplified by simply placing a transmitter in the package which
continuously is transmitting a radio signal. This radio signal
could be monitored by a receiver, thus constantly providing
adequate surveillance for the freight package. However, constantly
operating a transmitter with sufficient output wattage to pass
through the truck strucure, etc., requires power in excess of
feasible present day sources. On the other hand, with the use of
the present invention, the receivers therein utilizing present day
equipment, e.g., solid state electronics transceivers or the like,
can be continuously operated over a long period of time, i.e.,
commensurate with realistic shipping schedules.
Implementation of the freight security system of the present
invention provides the security personnel with a positive means of
providing electronic surveillance of the particular freight
package. The concept of the present invention is to plant a unique
transceiver in the freight package which responds with a coded
signal when properly interrogated, i.e., with a coded radio
frequency. The system includes a second transceiver which is
monitored by security personnel, and which is positioned at a
strategic location. The monitored transceiver may be automatically
triggered each time a conveyance means, e.g., a truck or the like,
passes a particular point or it may be triggered manually.
Triggering the monitored transceiver causes the transmitted carrier
frequency to be modulated with a first coded audio signal. The
planted transceiver responds with a second coded signal, if the
first signal was of the proper frequency. The monitored transceiver
includes a plurality of decoding networks and a plurality of neon
lights which respectively respond to signals accepted by the
decoding networks. Each light and associated decoding network
monitors a separate freight package for purposes of alerting the
security personnel when unauthorized movement of the freight
package is occurring. The system has the capability of
simultaneously safe-guarding numerous packages, e.g., 50 or more,
positioned at one location. Additionally, the system is capable of
discriminating or pinpointing the particular conveyance means that
is carrying the freight package.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of the freight security system of the
present invention.
FIG. 2 is a schematic drawing of a solid state transceiver, the
switching mechanism for changing the transceiver from the receiving
mode to the transmitting mode, the speaker, and the microphone
being deleted. The interconnecting circuitry terminates at a plug
which facilitates connecting the transceiver to the components
schematically depicted in FIG. 3 or the components schematically
depicted in FIG. 4.
FIG. 3 is a schematic of the components peculiar to the equipment
monitored by the security personnel. The interconnecting circuitry
terminates at a plug which connects with the plug depicted in FIG.
2.
FIG. 4 is a schematic of the components peculiar to the equipment
which is intended to be planted in a freight package. The
interconnecting circuitry terminates at a plug which is intended to
be connected to the plug depicted in FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The freight security system of the present invention is character
referenced in FIG. 1 of the drawings by the numeral 11 and
generally comprises at least one base transmitting and receiving
station 13 and a plurality of portable solid state transponders 15
(one being shown in FIG. 1). It should be understood that since
each of the plurality of transponders are identical one with the
other, it is considered expedient to depict a singular transponder
for fully describing the system.
The base station 13 generally comprises an activating apparatus 17
for initially activating a trigger circuit 19 which simultaneously
triggers or causes to be energized a typical transmitter circuit 21
and a unique encoder circuit 23. The audio frequency output of the
encoder 23 is modulated with the transmitting carrier frequency.
The base station 13 also includes a typical receiver circuit 25
having a unique demodulated audio frequency output coupled to a
plurality of decoder circuits 27, 29, 31. It should be pointed out
that the system 11 preferably includes at least one decoder circuit
for each transponder 15. In this regard, the system 11 preferably
comprises numerous substantially identical decoder circuits, e.g.,
upwards of 50, and for expediency three are conveniently depicted
to fully describe the system 11.
The base station 13 additionally includes a plurality of amplifier
circuits 33, 35, 37 which respectively respond to the decoder
circuits 27, 29, 31 under prescribed circumstances yet to be
disclosed. The outputs of the amplifiers 33, 35, 37 are coupled to
respective relays 39, 41, 43 which, when energized, cause
respective indicators 45, 47, 49, e. g., neon lights or the like,
to be energized.
The transponder 15 generally comprises a typical receiver circuit
51 for demodulating the encoded audio frequency which is coupled to
a decoder circuit 53. The output from the decoder 53 is coupled to
an amplifier circuit 55 and the output from the amplifier 55 is
coupled to a trigger circuit 57. The transponder 15 also includes
an encoder circuit 59 and a typical transmitter circuit 61, both of
which are energized simultaneously by the trigger circuit 57.
Referring still to FIG. 1 of the drawings, the following principle
of operation will serve as a general overview for the system 11 of
the present invention. The concept of the present invention is to
plant a transponder 15 into a box of package 62 (a portion only
being shown in FIG. 1) which is intended to be safe-guarded against
theft while in transit and/or while sitting at a dock site. The
system 11 will alert security personnel to the fact that this box
62 is being moved past a certain predetermined location. It should
be understood that the transponder 15 includes a self-contained
power supply and that the receiver 51 is placed in an "on" position
when planted. It should be further understood that the security
system 11 of the present invention may be adapted to any conveyance
means; however, in order to simplify the disclosure of the
preferred embodiment, the trucking industry will herein be used as
an example. The system is intended for operation on a frequency of
26.995 megacycles, which is designated Class C operation.
Accordingly, the transmitters 21, 61 are tuned so as to have a
carrier frequency 63 within this range. Obviously the receivers 25,
51 are also tuned to the carrier frequency 63 as above-described.
There are numerous operational procedures and/or physical layouts
for implementing the system 11 of the present invention.
Accordingly, the following disclosure is intended to be one
example:
The dock site (not shown) referably is provided with a guardhouse
which houses the security personnel and the base station 13. All
outgoing trucks (not shown) are funneled past a predetermined point
which is provided with an elongated resilient tubular member 65, e.
g., a rubber hose or the like, which terminates at the one end with
a closure means, e.g., a plug or the like, and communicates at the
other end with an enclosed bellows assembly 67. When the truck
passes over the air hose 65, the captured air displaces the bellows
assembly 67, closing the switch 69.
A terminal 71 is connected to a power source and closing the switch
69 activates the triggering circuit 19. The triggering circuit 19
can also be activated manually by the security personnel by closing
a switch 73 which is physically located within the guardhouse,
i.e., preferably on the cabinet structure (not shown) housing the
electronic components. The trigger circuit simultaneously energizes
the transmitter 21 and the encoder 23. The encoder 23 being an
audio oscillator, oscillates at a very closely controlled audio
frequency, e.g., 907.5 cycles per second, which modulates the
carrier frequency 63.
In the event the truck which caused the activating apparatus 17 to
operate does not contain the package having the transponder 15
planted therein, the sequence is thusly terminated.
However, in the event the truck which caused the activating
apparatus 17 to operate is carrying the package having the
transponder 15 planted therein, the receiver 51 thereof will
demodulate the encoded audio frequency, e.g., 907.5 cps, which in
turn is coupled to the decoder 53. The decoder 53, being tuned to
accept or pass the frequency of 907.5, passes a signal on to the
amplifier 55. The amplifier 55 increases the strength of the signal
and activates the trigger circuit 57. The trigger circuit
simultaneously energizes the encoder 59 and the transmitter 61. The
encoder 59 modulates the carrier frequency 63 with a second very
closely controlled audio frequency, e.g., 892.5 cycles per second,
which is transmitted back to the base 13 and is received by the
receiver 25.
The receiver 25 demodulates the audio frequency 892.5 from the
carrier frequency 63 and this audio output is connected to the
plurality of decoders 27, 29, 31. A decoder 27 is tuned to a
precise audio frequency, e.g., 862.5; the decoder 29 is tuned to a
precise audio frequency, e.g., 877.5; and the decoder 31 is
likewise tuned to a precise audio frequency, e. g., 892.5. In other
words, regardless of the number of decoders contained in the system
11, each decoder preferably is tuned to its individually unique
audio frequency. The audio output frequency 892.5 from the receiver
25 is simultaneously felt at the decoders 27, 29 and 31. The
decoders 27, 29 reject this frequency, however, the decoder 31
accepts or passes the frequency to its individual amplifying
circuit 37.
The output from the amplifier 37 is coupled to the relay 43 which
in turn energizes the neon light 49. The security personnel, being
familiar with the scheduled departure of the box 62 having the
planted transceiver therein are alerted to the fact that the box in
question is in fact on the truck being interrogated. In the event
the box is being legally transported, the truck merely moves on
through the control point to its destination or to other
interrogation stations 13. The interrogation stations 13 may be
mobile so as to interrogate the truck in transit in accordance with
detailed operating procedures peculiar to the conveyance means. On
the other hand, in the event the box containing the transceiver 15
is being illegally transported, the security personnel obviously
take the appropriate corrective measures. These corrective measures
alluded to may involve lengthy numerous detailed procedures and/or
other mobile interrogators 13 for maintaining surveillance of the
package containing the transponder 15, so as to apprehend other
involved individuals, etc.
The receiver 51 and the transmitter 61 may be two separate
components, or they may be combined into a suitable single
transceiver such as the Realistic Model No. TRC-45, which is a
product of Radio Shack a division of Tandy Corporation. This
transceiver is a two watt, ten transistor citizens band device and
is schematically depicted in FIG. 2 of the drawings. FIG. 2 of the
drawings substantially is a copy of the schematic contained in the
Realistic Model No. TRC-45 catalog No. 21-130.
The transmitter 21 and the receiver 25 of the base station 13 may
be two separate components, or they too may be combined into a
single transceiver similar to the Realistic TRC-45, accordingly, a
transceiver of the type schematically depicted in FIG. 2 is
intended to be used at the base station 13 and a similar one with
the transponder 15.
However, it may be desirable that the transceiver containing the
transmitter 21 and the receiver 25 for the base 13 have a greater
wattage output, e. g., 20 watts or the like. Numerous transceivers
of varying tradenames and wattage outputs are commercially
available, and the principle of operation is well known.
Accordingly, a brief description of the transceiver depicted in
FIG. 2 will suffice for present purposes and references should be
made to the technical data provided by the manufacturer of the
particular transceiver used for a more detailed description of the
particular transceiver incorporated.
FIG. 2 depicts a plug 75 having many contact pins, e. g., a cannon
plug or the like, for expedience in disclosing the interconnecting
circuitry between the respective FIGS. 2 and FIGS. 3 and 4. In
other words, the plug 75 is optional and is used merely as a
convenience in explaining the drawings. The above explanation
obviously pertains to a plug 77 (FIG. 3) and a plug 79 (FIG. 4), i.
e., the cannon plug 75 being a female type plug having structure
suitable for receiving either of the two male type plugs 77, 79.
Accordingly, the three plugs 75, 77, 79 will have identically
numbered pins.
Pin 81 carries the input signal to the receiver from the
appropriate antenna. Pin 83 carries the output signal from the
transmitter to the appropriate antenna. It should be understood
that the general description of the receiver cannot conveniently be
directed towards either the base station 13 or the transponder 15
since the structure for the transceiver incorporated at the base
station and the structure of the transceiver incorporated with the
transponder are different; therefore, a detailed disclosure of the
components peculiar to the base station 13 and the transponder 15
will subsequently be disclosed.
Pin 85 carries the volume control feedback for the receiver. Pin 87
carries the power input for the receiver from the battery or other
power supply. Pin 89 carries the power input to the final audio
stages and/or the modulation stage of the transmit position from
the battery or other power supply. Pin 91 carries B+ supply for
transmitter 21. Pin 93 carries the receiver output; pin 95 carries
the second conductor for the power input from the battery or other
power supply. Pin 97 carries the encoder input signal or audio
frequency to the transmitter. Pin 99 carries the second conductor
from the battery for certain components while the transceiver is in
the receiver mode. Pin 101 carries the second conductor from the
battery or for various components while the transceiver is in the
trasnmitting mode.
The potentiometer 103 (FIG. 2), being the volume control for the
receiver, varies the amplitude of the audio signal from the
appropriate receiver, i.e., receiver 25 or receiver 51, to the
respective decoder. The potentiometer 103, accordingly, provides
the system 11 with a range control, i.e., enabling the base station
13 to adjust the range so that it is restricted to interrogating
trucks within a predetermined radius. The radius referred to would
obviously include a space which could conceivably be occupied by
only one truck, thus precluding the likelihood of inadvertently
interrogating two trucks simultaneously.
Referring now to FIG. 3 of the drawings wherein the components
peculiar to the base station 13 and which are married to a
transceiver such as depicted in FIG. 2, by connecting the plug 75
to the plug 77, are schematically illustrated. A power supply 105
preferably having a 12 volt direct current output is symbolized in
the drawing as being a battery, however, the power supply 105 may
be a 12 volt D. C. power supply derived from 115 volt alternating
current in order to enhance reliability. In this regard, a
preferred arrangement wherein an emergency backup of a 12 volt
battery which is automatically connected to the system 11 in the
event of a power failure is advisable. The positive terminal of the
power supply 105 is grounded and leads to a single pole single
throw master switch 107.
Closing the switch 107 completes the circuit to a three-way
junction which completes the circuit to: First, a push-button
two-point "break" switch 109; secondly, a contact 111 of a four
pole double throw relay 113; thirdly, pin 89 of the cannon plug 77.
It should be understood that the numerous relay schematically
depicted in the drawings are shown in a de-energized position.
The negative side of the power supply 105 is connected to a
negative bus bar 115. A conductor 117 connected at the one end of
the bus bar 115 leads to the two activating switches 69, 73. The
switches 69, 73 are single pole single throw switches connected in
parallel so that closure of either completes the circuit to a
single pole double throw relay 119, a component of the trigger
circuit 19. Energizing the relay 119 completes the circuit between
the contacts 121, 123 which places the 12 volts on a 100 mfd
capacitor 125, thus charging the capacitor 125. The activating
switch, i.e., either switch 69 or switch 73, is held in a closed
position only momentarily and then returned to the open position.
Accordingly, the relay 119 is energized briefly but sufficiently to
charge the capacitor 125. The relay 119, being de-energized,
returns to the normal position which completes the circuit between
a contact 127 and the contact 123. The capacitor 125, having been
charged, acts as a power supply and sends current through 15 K
resistor 129 for a period of time selectively determined by the
values chosen for the capacitor 125 and the resistor 125.
A 15 K ohm resistor 131 is connected at the one end to the junction
of the capacitor 125 and the resistor 129 and at the other end to
the base 133 of a GE-2 transistor 135, the transistor 135 having
the base 133, the emitter 137 and the collector 139. The voltage
felt across the biasing resistor 131 on the base 133 causes the
collector 139 to pull electrons from the emitter 137. In other
words, the circuit for the above-mentioned electron or current flow
is through a conductor 141 having the one end thereof connected to
the collector 139 and the other end connected to the winding of the
relay 113, the other end of the winding 113 being connected to the
negative bus bar 115. Accordingly, current flows from the power
supply 105 through the transistor 135 and the relay 113, thus
energizing the relay 113 for a predetermined period of time.
The function of the relay 113 is to switch the base station 13 from
a receiving mode to a transmitting mode and from the transmitting
mode back to the receiving mode. In other words, the receiver 25 is
normally on while the relay 113 is de-energized, and energizing the
relay 113 turns on receiver off and activates the transmitter 21
for a predetermined period of time. This predetermined period of
time is calculated by the values selected or the time constant of
the capacitor 125 and the resistor 129. I prefer to have the
transmitter activated for approximately five seconds before the
relay 113 returns the base station 13 to the receiver mode.
The relay 113, when in the receive mode, completes the circuit from
a transmitting and receiving antenna 143 through a pair of contacts
145, 147, the contact 147 having one end of a conductor connected
thereto, the other end of which is connected to the pin 81 of the
plug 77. Secondly, the relay 113, when de-energized, completes the
circuit between the pins 85, 97 of the plug 77 through a pair of
contacts 149, 151. Thirdly, the relay 113 delivers B+ from the
power supply 105 to the pin 87 of the plug 77 through the
aforementioned contact 111 and a contact 153. Fourthly, the
de-energized relay 113 connects B- of the power supply 105 to the
pin 99 of the plug 77 through a pair of contacts 155, 157.
When the relay 113 is energized, i.e., the base station 13 being in
the transmit mode, the antenna 143 is connected to the output of
the transmitter through the pin 83 of the plug 77 and a pair of
contacts 145, 159. Secondly, the output of the encoder circuit 23,
e.g., an audio frequency of 907.5 cycles per second, modulates the
carrier frequency of the transmitter 21 by having one end of a
conductor 160 connected to an output terminal 161 of the encoder
circuit 23 and the other end connected to a contact 163 of the
relay 113, a second conductor 162 completes the circuit from the
contact 149 to the pin 97 of the plug 77. Thirdly, B+ is applied to
a positive bus bar 165 of the encoder circuit 23 by having one end
of a conductor 166 connected thereto and the other end being
connected to a contact 167 of the relay 113, i. e., the contact 111
being connected to B+ as previously described. Fourthly, the
negative bus bar 115 is connected to the pin 101 of the plug 77
through a contact 169 of the relay 113, i. e., the contact 155
being connected to the bus bar 115 as previously described.
The heart of the encoder circuit 23 is a subminiature piezoelectric
tuning fork 171 manufactured under the tradename of "Microfork"
which is manufactured by the Murato Manufacturing Co., Ltd., of 160
Broadway, N.Y., N.Y. The microfork used in the present invention
for the encoder is a model EFM and is a newly designed tuning fork
subminiaturized from Pieleforks. This model is now widely used for
bellboy systems, selective calling, remote control and tone control
of electronic musical instruments where compactness, reggedness and
economy are required. The microfork 171, having a length slightly
greater than one inch and transversal dimensions of less than
one-third inch, operates in the frequency range of 360 - 2,900 cps
with an accuracy of 0.5 cps up to 999 cps and .sub.-1 cps from
1,000 - 2,900 cps. The encoder circuit 23 is substantially
identical with the test circuit included in the technical data
provided by the Murata Manufacturing Co. pertaining to the
microfork 171.
The microfork 171 has three predetermined terminals P, S and G,
i.e., the preferred connection is: The terminal P is the output
terminal; the terminal S is the input terminal; and the terminal G
is the ground terminal. The encoder circuit 23 includes: (1) A
negative bus bar 173, connected by a conductor 174, to the power
supply negative bus bar 115. (2) A capacitor 175 having a value
determined by the frequency selected, i. e., the value is 0.005 mfd
for frequencies under 1,000 cps and the value is 0.001 mfd for
frequencies about 1,000 cps. The capacitor 175 has one side thereof
connected to the positive bus bar 165 and the other side connected
to the input terminal S of the microfork 171, i. e., the input
terminal S leading to a common point 177. (3) A 100 K ohm resistor
179 having one end thereof connected to the common point 177 and
the other end connected to the negative bus bar 173. (4) A GE-2
transistor 181, having a base 183, an emitter 185 and a collector
187, with the base thereof being connected to the common point 177,
the collector 187 being connected to the negative bus bar 173 and
the emitter 185 being connected to the output terminal 161 of the
encoder circuit 23. (5) A 10 K ohm resistor 189 having one end
thereof connected to the output terminal 161 of the encoder circuit
23 and the other end connected to the positive bus bar 165. (6) A 1
K ohm resistor 191 having one end thereof connected to the output
terminal 161 and the other end connected to the one end of a 10 mfd
capacitor 193. (7) A 33 K ohm resistor 195 having one end thereof
connected to the negative bus bar 173 and the other end connected
to a common point 196. (8) A 4.7 K ohm resistor 197 having one end
thereof connected to the common point 196 and the other end
connected to the positive bus bar 165. (9) The other end of the
capacitor 193 is connected to a point between the junction of the
resistors 195, or in essence the common point 196. (10) A second
GE-2 transistor 199, having a base 201, an emitter 203 and a
collector 205, has the base thereof 201 connected to the common
point 196, the collector 205 connected to a common point 207, and
the emitter 203 connected to a common point 209. (11) A 5.6 K ohm
resistor 211 has one end thereof connected to the common point 207
and the other end connected to the negative bus bar 173. (12) A
conductor 213 has one end thereof connected to the common point 207
and the other end connected to the P terminal or the output
terminal of the microfork 171. (13) A 1 K ohm resistor 215 has one
end thereof connected to the common point 209 and the other end
connected to the positive bus bar 165. (14) A 10 mfd capacitor 217
has one end thereof connected to the common point 209 and the other
end connected to the positive bus bar 165.
The above network of electronic components comprises an audio
oscillator or encoder circuit 23 having a closely controlled
frequency output, e.g., 907.5 cps .+-. 0.5 cps. The carrier
frequency 63 is modulated with this frequency, i. e., 907.5 cps,
when the relay 113 is energized, as above-described. A 0.0047 mfd
capacitor 219, having the one end thereof connected to the negative
bus bar 173 and the other end connected to the positive bus bar
165, is optional and is used herein to electrically isolate the
transmitter 21 and receiver 25 (FIG. 2), having a negative ground,
from the circuitry schematically depicted in FIG. 3 which has a
positive ground.
Thus far we have the base station 13 sending a coded signal, i. e.,
907.5 cps, from the transmitter 21 to the antenna 143. The carrier
frequency 63 radiates outwardly from the antenna 143 in all
directions and assuming that a truck (not shown) having a carton 62
containing the planted transponder 15 therein is physically located
at the interrogation point, the receiver 51 of the transponder 15
will receive the transmission. The receiver 51 detects of
demodulates the coded signal, i.e., 907.5 cps, which is delivered
to the pin 93 of the plug 75 (FIG. 2).
Referring now to FIG. 4 of the drawings wherein it may be seen that
a conductor 220, having one end thereof connected to the pin 93 of
the plug 79 and the other end connected to the primary windings of
a step up transformer 221, carries the output from the receiver 51.
It should be pointed out that normally the output of a receiver is
delivered to a step down transformer which steps up the current
sufficiently to drive the speaker element. The current requirements
for the embodiment of the present invention are minimum; however,
the voltage or amplitude of the signal is stepped up across the
transformer 221. A conductor 222, having the one end thereof
connected to the primary of the transformer 221 and the other end
connected to a common point 223, completes the circuit for the
input signal, i.e., the common point 223, having a B- potential yet
to be described, is connected to the pin 95 of the plug 77.
The transponder 15 has a transmitting and/or receiving antenna 225
and a four pole double throw relay 227 having a function
substantially identical to the relay 113 for the base station 13,
above-described. The relay 227, when de-energized, places the
transponder 15 in the receiver mode by connecting the antenna 225
to the receiver 51 through a pair of contacts 229, 231, i.e., a
conductor connecting the antenna 225 to the contact 229 and a
second conductor connecting the second contact 231 to the pin 81 of
the plug 79. The pins 85, 97 of the plug 79 are connected by a pair
of contacts 233, 235, i.e., a conductor connects the pin 97 to the
contact 233 and a second conductor connects the pin 85 to the
contact 235. The pin 87 is connected to a B+ potential, yet to be
described, by a pair of contacts 237, 239, i.e., a conductor
connects the pin 87 to the contact 239 and a second conductor
connects a common point 240 to the contact 237. B+ is applied to
the common point 240 by having the one end of a conductor 242
connected to B+ and the other end thereof connected to the common
point 240.
It should be pointed out at this time that the transponder 15
includes a power supply 241, e.g., preferably a 12 volt battery or
ten individual cells connected in series so as to deliver 12 volts
direct current. The positive side or B+ of the power supply 241
leads to a master "on" or "off" switch 243 which applies B+ to the
above-mentioned common point 240. It should be observed that the
positive side of the power supply 241 is grounded. The negative
side or B- of the power supply 241 is connected to a negative bus
bar 245 and a conductor 246 connects the above-mentioned common
point 223 to the bus bar 245. A pair of contacts 247, 249 completes
the circuit between the negative bus bar 245 and pin 99, i.e., a
conductor 250 connects the bus bar 245 and the contact 247 and a
conductor 252 connects the pin 99 and the contact 249.
The transponder 15 is placed in the transmitting mode when the
relay 227 is energized. Energizing the relay 227: first places the
output from the transmitter 61 to the pin 83 of the plug 79. The
pin 83 is connected to the antenna 225 by a contact 251 and the
contact 229, i.e., a conductor connects the pin 83 to the contact
251. Secondly, the pin 97 is connected to an output terminal 253 of
the encoder circuit 59, i.e., a conductor 254 connects the output
terminal 253 to a contact 255 of the relay 227. Thirdly, a common
point 257 is connected to B+ of the power supply 241 by a contact
259, i.e., a conductor connects the contact 259 to the common point
257, the contact 249 being tied to B+ as previously described.
Fourthly, a contact 261 connects the negative bus bar 245 or B- to
th pin 101 of the plug 79, i.e., a conductor connects the contact
261 to the pin 101 and the conductor 250 having the one end thereof
connected to the contact 247 is connected at the other end to the
bus bar 245 as previously described.
Continuing now with the normal sequence of operation and still
referring to FIG. 4 of the drawings wherein the output, i.e., 907.5
cps, of the receiver 51 was placed on the primary winding of the
transformer 221, the relay 227 being de-energized. One end of the
secondary winding of the transformer 221 is connected to the P or
output terminal of a receiving type microfork 263. It should be
explained that the microfork model EFM is provided by the Murata
Manufacturing Co. in two separate configurations: a transmitter or
sender type microfork designated EFM-S and a receiver type, for
responding to or passing a narrow width of audio frequencies,
designated EFM-R. The previously described specifications for
microforks are directed to both the EFM-R and the EFM-S types. It
should be noted that the other end of the secondary winding of the
transformer 221 is void of the usual ground connection, i.e.,
having interelectrode capacitance only or in other words the
circuit for the secondary is open which allows the voltage from the
secondary to be felt at the terminal P but does not permit current
flow through the microfork 263.
The microfork 263, as above described, is manufactured or fixed to
be responsive to a predetermined narrow band of audio frequencies
and to reject all other frequencies. Since the base station 13 is
transmitting a carrier frequency 63 which is modulated by the
encoder 23 with an assumed frequency of 907.5 cps .+-. 0.5 cps, the
microfork 263 must be selected to be responsive to the assumed
frequency of 907.5 cps. The narrow band width of frequencies which
the microfork 263 will respond to is approximately 902 cps - 1,002
cps, i.e., the microfork 263 will reject any other frequency.
The G terminal of the microfork 263 is connected to ground, and
assuming that the incoming frequency was within the above-specified
range, the microfork will pass a minute signal from the S terminal
to the audio amplifying circuit 55.
The first stage of the audio amplifying circuit 55 comprises: (1) A
GE-2 transistor 265, having the usual base 267, the collector 269,
and the emitter 271. The minute signal from the microfork 263 is
coupled to the base 267. (2) A 100 K ohm biasing resistor 273
having one end thereof connected to the base 267 and the other end
connected to B- or the negative output of the power supply 241,
i.e., a conductor 275 having one end connected to the negative bus
bar 245, and the other end terminating at a common point 277 which
receives the one end of a second conductor 279, the other end being
connected to a second common point 281 which receives the one end
of a third conductor 283, the other end of which is connected to a
third common point 285 which receives the one end of a fourth
conductor 287, the other end being connected to a fifth common
point 289 which receives the other end of the resistor 273. The
collector 269 of the transistor 265 is also connected to the common
point 289. (3) A 10 K ohm bias resistor 291 has the one end thereof
connected to ground, and the other end connected to a common point
293. The emitter 271 of the transistor 265 is also connected to the
common point 293. The amplified output of this first stage is
coupled to a second amplifying stage by a 10 mfd electrolytic
capacitor 295.
The second amplifying stage comprises: (1) A second GE-2 transistor
297, having the usual base 299, a collector 301, and an emitter
303, The base 299 of the transistor 297 is connected to a common
point 305. The coupling capacitor 295 has one end thereof connected
to the common point 293 and the other end connected to the common
point 305 which places the amplified signal of the first stage onto
the base 299 of the second stage transistor 297. (2) A 15 K ohm
resistor 307 and a 39 K ohm resistor 309 comprise a voltage divider
network by having the one end of the resistor 309 connected to the
common point 285 and the other end connected to the common point
305, also, the one end of the resistor 307 being connected to the
common point 305 and the other end thereof being connected to
ground. (3) A 4.7 K ohm biasing resistor 311 having one end thereof
connected to the common point 281 and the other end being connected
to the collector 301 of the transistor 297. (4) A 1 K ohm biasing
resistor 313, having one end thereof connected to ground and the
other end connected to the emitter 303. (5) A 10 mfd electrolytic
capacitor 315 connected in parallel with the resistor 313, i.e.,
the one end of the capacitor 315 being connected to one end of the
resistor 313, and the other end thereof being connected to ground.
The capacitor 315 is a bypass capacitor, i.e., prevents the signal
from going to ground.
A 10 mfd electrolytic capacitor 317 couples the output signal from
the second stage of the amplifier circuit 55 to a rectifier circuit
319, comprising a pair of 1 N 34 diodes 321, 323. The diode 321 has
the usual anode 325 and cathode 327 and the diode 323 has the usual
anode 329 and the cathode 331. The anode 325 is connected to the
cathode 331 at a common point 333, the cathode 327 is connected to
ground, and the anode 329 is connected to a second common point
335. The coupling capacitor 317 has the one end thereof connected
to the collector 301 of the transistor 297 and the other end
connected to the common point 333.
A coupling means 337 couples the rectified output of the rectifier
319 to the triggering circuit 57. The coupling means 337 comprises:
(1) A GE-2 transistor 339, having the usual base 341, the collector
343, and the emitter 345. (2) A 22 K ohm biasing resistor 347. (3)
A 10 mfd electrolytic capacitor 349. The one end of the resistor
347 is connected to the common point 335 and the other end is
connected to ground. The filtering capacitor 349 filters the signal
onto the transistor 339, i.e., the signal now being a steady
substantially DC voltage. The one end of the capacitor 349 is
connected to a point having the same potential as does the common
point 335 and the other end of the capacitor 349 is connected to
ground. The base 341 is connected to this point, i.e., having the
same potential as does the common point 335. The coupling means 337
also includes a 68 ohm biasing resistor 351 having the one end
thereof connected to the emitter 345 and the other end connected to
ground.
This signal or steady DC voltage being applied to the base 341 of
the transistor 339 causes current to flow from the emitter 345 to
the collector 343, i.e., the path of current flow being through the
resistor 351 to ground. Thence the current flows to the positive
side of the power supply 241, thence through the power supply or
out the negative bus bar 245 through the conductor 275 to the
common point 277, thence through a conductor 353 past a common
point 355 to one end of the winding of a single pole double throw
relay 357, thence out the other side of the relay 357 through a
conductor 359 to the collector 343, i.e., the relay 357 being a
part of the trigger circuit 57.
Thus, the relay 357 is energized, which charges a 250 mfd
electrolytic capacitor 361, i.e., the circuit being completed
through a pair of contacts 363, 365, the contact 363 being at the
same potential as the common point 355 or having a negative 12 volt
potential, thence through a conductor 367 which connects one end of
the capacitor 361 to the contact 356 thence through a conductor 369
which connects the other end of the capacitor 361 to ground, thence
from ground to the positive side of the power supply 241, all being
additional components of the trigger circuit 57. The relay 357 will
remain energized so long as the transistor 339 feels the constant
voltage from the filtering circuit 319; howver, the base station 13
triggering circuit 19 preferably is programmed so as to key the
transmitter 21 and trigger the encoder 23 for a duration of 5
seconds, after which time it goes back to the receive mode.
Accordingly, the output of the receiver 51 of the transponder 15
will also have a duration 1f 5 seconds, after which time the signal
across the transformer 221 ceases since the voltage felt on the
microfork 263 is nil, thence the input to the amplifier circuit 55
is nil, thence the input to the filtering network 319 is nil which
causes current to cease flowing from the emitter 345 to the
collector 343 of the transistor 339 which de-energizes the relay
357 after the 5 second duration.
When the relay 357 is de-energized, the charged capacitor 361,
acting as a power source, starts to discharge through the conductor
367, thence from the contact 365 to a third contact 371, thence
through a conductor 373, having the one end thereof connected to
the contact 371 and the other end connected to a common point 375,
thence through an 80 K ohm resistor 377, having one end thereof
connected to the common point 375 and the other end connected to
ground, thence through the conductor 369 to the other side of the
capacitor 361, all being further components of the trigger circuit
57. Accordingly, the common point 375 assumes a negative potential
equal to the charge on the capacitor 361.
The triggering circuit 57 also includes a GE-2 transistor 379,
having the usual base 381, the collector 383, and the emitter 385,
and a 15 K ohm bias resistor 387. The voltage at the common point
375, being biased by the bias resistor 387 is felt on the base 381
of the transistor 379 which causes current flow through the
transistor 379, i.e., the path of current flow being from the
emitter 385 down through a conductor 389 to ground, thence to the
positive side of the power supply 241, thence out the negative bus
bar 245 through a conductor 391, having one end thereof connected
to the negative bus bar 245 and the other end connected to the
relay 227, thence through the winding of the relay 227, thence
through a conductor 395, having one end thereof connected to the
relay 227 and the other end connected to the collector 383.
Thus, the relay 227 is energized while the capacitor 361 is
discharging, i.e., the period of time being selectively determined
by the values chosen for the capacitor 361 and the resistor 377. In
this instance, the preferred period of time for the relay 227 to
remain energized is 15 seconds. It should be understood that it may
be desirable in other embodiments to have the relay 227 energized
for other periods of time which are considered to be within the
full intended scope and spirit of the present invention.
Energizing the relay 227 deactivates the receiver 51 and
simultaneously keys the transmitter 61 and triggers the encoder 59,
i.e., the contacts 229, 251 place the antenna 225 in communication
with the pin 83 of the plug 79, the contacts 233, 255 place the
output terminal 253 of the encoder 59 in communication with the pin
97, the contacts 237, 259 places the positive side of the power
source 241 or B+ on the common point 257 (the common point 257
communicating with the pin 91 and a positive bus bar 397 of the
encoder circuit 59), and the contacts 247, 261 place the negative
bus bar 245 in communication with the pin 101.
Accordingly, the transmitter 61 commences transmitting the carrier
frequency 63 and the encoder 59, having the bus bar 397 energized,
commences oscillating at a predetermined audio frequency which is
modulated or mixed with the carrier frequency 63. The audio
frequency of the encoder 59 is determined and closely controlled or
stabilized by a subminiature piezoelectric tuning fork, e.g., a
microfork Model EFM-S 399. It should be pointed out that the
microfork 171 for the encoder 23 and the microfork 263 for the
decoder 53 are always tuned to the same frequency, e.g., 907.5 cps,
irrespectively of the number of transponders 15 incorporated with
the system 11. However, each transponder 15 will have its unique
encoder 59 frequency, e. g., 892.5 cps, and the base station 13
will have a decoder circuit tuned to that unique frequency, e.g.,
the decoder 31 as previously described.
In this regard, the microfork 399 is tuned to the frequency
peculiar to the specific transponder 15, in this case 892.5 cps.
The encoder circuit 59 (FIG. 4) is identical to the encoder circuit
23 (FIG. 3), i.e., the frequency of the microfork 399 differs from
that of the microfork 171, but the respective interconnecting
circuits and values of their components are identical. Accordingly,
the previous detailed disclosure of the encoder 23 is intended to
encompass the encoder 59. The output of the encoder 59, i.e., 892.5
cps, leaves the encoder 59 from the output terminal 253 through the
conductor 254, havine one end thereof attached to the terminal 253
and the other end connected to the contact 255, and enters the
transmitter 61 through the pin 97 of the plugs 75, 79 where it
modulates the carrier frequency 63.
The base station 13 receives this carrier frequency 63 on the
receiver 25 which detects or demodulates the encoder frequency,
i.e., 892.5 cps, and this signal is placed on the pin 93 of the
plugs 75, 77 (FIGS. 2 and 3).
Referring now to FIG. 3 of the drawings, wherein it should be
explained that the relay 113 is in the de-energized position, the
incoming signal from the receiver 25 is between the pins 93, 95 of
the plug 77 which are in communication with the primary windings of
a step-up transformer 403, e.g., having a ratio of 50 : 1. One end
of the secondary winding of the transformer 403 is grounded, and
the other end is connected to a series of decoder circuits 27, 29,
31, i.e., the decoder 27 comprising a subminiature piezoelectric
"receiving" tuning fork 405, e.g., microfork model EFM-R, the
decoder 29 comprising a subminiature piezoelectric "receiving"
tuning fork 407, e.g., a microfork model EFM-R, and the decoder 31
comprising a subminiature piezoelectric "receiving" tuning fork
409, e.g., a microfork model EFM-R. The microforks 405, 407, 409
are in parallel one with the other, i.e., the P or output terminal
of each is connected to a common point which is in communication
with the secondary of the transformer 403 and the G or ground
terminal of each is connected to ground. The S or input terminals
of the respective microforks 405, 407, 409 are connected to the
amplifier circuits 33, 35, 37.
The amplifier circuits 33, 35, 37 are individually identical to the
amplifier circuit 55 (FIG. 4) previously described. Consequently,
the detailed disclosure of the amplifier circuit 55 is intended to
encompass the amplifier circuits 33, 35, 37, i.e., the value of the
components and the interconnecting circuitry are identical.
The respective outputs from the amplifiers 33, 35, 37 are coupled
to a plurality of rectifier circuits 411, 413, 415. The rectifier
circuits 411, 413, 415 are individually identical to the rectifier
circuit 319 (FIG. 4). Consequently, the detailed disclosure
pertaining to the rectifier circuit 319 is intended to encompass
the rectifier circuits 411, 413, 415, additionally, the respective
coupling capacitors 317, 317', 317", 317'" are identical one with
the other.
The output of the respective rectifier circuits 411, 413, 415 are
coupled to the relays 39, 41, 43 by a plurality of coupling means
417, 419, 421. The coupling means 417, 419, 421 are individually
identical to the coupling means 337 (FIG. 4). Consequently, the
detailed disclosure pertaining to the coupling means 337 is
intended to encompass the plurality of coupling means 417, 419,
421.
The relays 39, 41, 43, being identical one with the other, are
double pole single throw holding relays for respectively energizing
the plurality of indicator means, e. g., the neon lights 45, 47,
49. Accordingly, a detailed description of each relay 39, 41, 43
would be redundant.
In order to follow the signal, i. e., 892.5 cps from the
transformer 403, it is necessary to assign a like frequency to one
of the plurality of the microforks 405, 407, 409. Therefore, the
microfork 409 is pretuned at the factory to the frequency of 892.5
cps and will pass a frequency within 5 cps of this frequency and
reject all others. In this regard, the microforks 405, 407 are
respectively tuned to a fixed frequency of 862.5 cps and 877.5 cps
and will pass frequencies within 5 cps of these fixed frequencies
and will reject all other frequencies.
The signal, i. e., 892.5 cps from the transformer 403, is
simultaneously felt at the microforks 405, 407 and 409. The
microforks 405, 407 reject this signal; however, the microfork 409
accepts or passes the signal to the S or input terminal. This
signal is received by the two stage audio amplifier circuit 37
which passes it through the coupling capacitor 317'" to the
filtering circuit 415. The filtered signal, i. e., a substantially
steady DC voltage, is coupled to the relay 43 by the coupling means
421, a conductor 359'" carrying the positive gate type signal to
the relay 43. Thus, the relay 43 is energized, completing the
circuit between the contacts 423, 425, 427, 429 thereof. The one
side of the winding of the relay 43 and one side of the neon light
49 are both tied to the negative bus bar 115. The contacts 427, 423
are connected to the switch 109 which is connected to the positive
side of the power supply 105. Energizing the relay 43 momentarily,
e. g., 15 seconds or the like, causes the contacts 423, 425 to
complete the circuit from the positive side of the power supply to
the winding of the relay 43, thus holding the relay 43 in an
energized position until it is manually de-energized by pushing the
pushbutton switch 109. At this same time, the circuit is complete
across the contacts 427, 429 which places the positive side of the
power supply on the other side of the neon light 49, thus causing
it to be energized until the switch 109 is manually pushed.
The illumination of the neon light 49 alerts the security personnel
to the fact that the package containing the transponder 15 is in
the fact in the truck or other means of conveyance being
interrogated.
Obviously, the neon lights 45, 47 are for other transponders 15
which may have been planted in other cartons. Additionally, the
base station 13 would include numerous neon lights (not shown) for
safe-guarding a like number of cartons, e. g., 50 or more,
From the foregoing, it will be seen that I am enabled to safe-guard
numerous freight packages against theft while in transit and/or
while sitting at a dock site.
Although the invention has been described and illustrated with
respect to a preferred embodiment thereof, it is to be understood
that it is not to be so limited since changes and modifications may
be made therein which are within the full intended scope of this
invention.
* * * * *