U.S. patent number 3,891,980 [Application Number 05/304,560] was granted by the patent office on 1975-06-24 for security systems.
This patent grant is currently assigned to Lewis Security Systems, Ltd.. Invention is credited to William Dudley Gilmour, John Lewis.
United States Patent |
3,891,980 |
Lewis , et al. |
June 24, 1975 |
**Please see images for:
( Certificate of Correction ) ** |
Security systems
Abstract
A security system controls admission of persons to protected
areas. An authorised person carries in his pocket a token which
generates at two discrete frequencies and when he approaches a door
leading to the restricted area, a sensor of his presence sends an
initiating signal to a control unit which examines whether the
required discrete frequencies are being generated and are being
picked up by inductive loops adjacent the door. If the correct
signals are being generated the door is automatically opened but if
not the door remains closed and an alarm may be given. The user
does not need to take his token from his pocket so that the effect
will be that the door will open automatically for authorised
persons.
Inventors: |
Lewis; John (London,
EN), Gilmour; William Dudley (Glastonbury,
EN) |
Assignee: |
Lewis Security Systems, Ltd.
(London, EN)
|
Family
ID: |
26256172 |
Appl.
No.: |
05/304,560 |
Filed: |
November 7, 1972 |
Foreign Application Priority Data
|
|
|
|
|
Nov 8, 1971 [GB] |
|
|
51724/71 |
May 16, 1972 [GB] |
|
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22898/72 |
|
Current U.S.
Class: |
340/5.62;
361/175; 902/4; 340/5.3; 340/10.5; 70/DIG.49; 361/183; 340/539.11;
340/539.1 |
Current CPC
Class: |
G08B
13/24 (20130101); G07C 9/00182 (20130101); G07C
9/27 (20200101); G07C 9/00571 (20130101); G08B
13/22 (20130101); Y10S 70/49 (20130101); G07C
2209/64 (20130101); G07C 2009/00777 (20130101) |
Current International
Class: |
G07C
9/00 (20060101); G08B 13/22 (20060101); G08b
013/18 () |
Field of
Search: |
;340/258D,258C,147F,280
;343/225 ;317/134 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Swann, III; Glen R.
Attorney, Agent or Firm: Brumbaugh, Graves, Donohue &
Raymond
Claims
What we claim as our invention and desire to secure by Letters
Patent is:
1. A security system including at least one portable token
embodying a generator and transmitter of oscillations at a
predetermined frequency, a pickup at a certain location and means
in the pickup for responding to the oscillations transmitted from
the token when the token is carried in any atatitude by a user who
comes to the location, a sensor responsive to arrival of a person
at the location, and a control unit rendered operative by response
of the sensor and having means for providing a local reference
signal, means responsive to the pick-up response and the local
reference signal for forming an output signal, and means receiving
the output signal for detecting whether the pickup is responding to
oscillations at the predetermined frequency, and to deliver a
control signal to dependence upon such detection.
2. A system as claimed in claim 1 in which the pickup comprises two
inductive loops and the control unit includes phase shifters for
shifting the phase of signals picked up by the different loops by
different phase angles, and means for combining the phase-shifted
signals.
3. A system as claimed in claim 1 in which the token is capable of
simultaneously transmitting oscillations at two different
predetermined frequencies and including means in the control unit
for detecting whether oscillations at both the predetermined
frequencies are being picked up by the pickup.
4. A system as claimed in claim 1 including a plurality of tokens
at least one of which is capable of transmitting oscillations at at
least one predetermined frequency and at least one other of which
is capable of transmitting oscillations at at least one different
frequency, and means in the control unit for detecting whether the
one predetermined frequency is present at one location and whether
the different frequency is present at another location.
5. A security system as claimed in claim 4 in which the control
unit is arranged to deliver a control signal whether the one or the
other frequency is present to be picked up at one of the
locations.
6. A system as claimed in claim 1 in which the or each token is
arranged to transmit continuously without requiring any action by
the person carrying it.
7. A security system as claimed in claim 1 additionally comprising
a socket for each token and a battery charger for automatically
charging batteries in the tokens when they are inserted in their
sockets.
8. A system as claimed in claim 1 in which the control unit
includes a local oscillator oscillating at a frequency displaced
from the predetermined frequency for producing beat frequency
pulses and a detector circuit for distinguishing between beat
frequencies above and below a certain limit.
9. A system as claimed in claim 8 in which the beat frequency
pulses are passed through a low pass filter in the control unit for
cutting off beat frequencies outside a permitted range.
10. A system as claimed in claim 9 including in the control unit a
counter gate for counting beat frequency pulses over a
predetermined time interval and means for detecting whether the
count achieved is greater or less than a predetermined count.
11. A system as claimed in claim 10 including means for the control
unit for detecting whether no pulses are received over an interval
and means connected to the counter gate and providing a wave signal
for delimiting the inverval.
12. A system as claimed in claim 10 including a logic circuit
arranged to give an accept signal for controlling the deterrent in
dependence on the count of the counter.
13. A system as claimed in claim 12 wherein the logic circuit
includes means for initiating a further detection cycle
automatically in response to no accept signal being given within a
predetermined time.
14. A system as claimed in claim 13 including means for giving no
alarm if, but only if, an acceept signal is given after at least
two detection cycles.
15. A system as claimed in claim 8 including in the control unit
means for modulating the local oscillator frequency by a few cycles
for a fraction of a detecting cycle and not for the remainder of
the cycle, means providing a wave signal for delimiting the
detecting cycle and means responsive to the wave signal for
delimiting fractions of the cycle.
16. A system as claimed in claim 15 including in the control unit
gates for counting beat frequency pulses in one sense for the
fraction of the cycle and in the other sense for the remainder of
the cycle.
17. A security system as claimed in claim 1 including a deterrent
and means responsive to the control signal for operating the
deterrent.
18. A system as claimed in claim 17 in which the deterrent
comprises a door having a lock arranged to be operated in response
to the control signal from the control unit.
19. A system as claimed in claim 17 in which the deterrent
comprises an alarm arranged to be operated in response to the
control signal from the control unit.
20. A security system as claimed in claim 1 including an exit loop
detector at an exit from premises and in which the control unit
responds to a signal from the exit loop detector due to a token
being taken through the exit.
21. A security system for operating a deterrent comprising:
a portable token for carrying within the system, the token having
means for generating and transmitting oscillations at two different
frequencies;
a loop system at a certain location in the system for providing an
output signal including the oscillation frequencies from the token,
the loop system having two inductive loops in substantially
perpendicular planes for picking up the oscillations from the token
when the token is carried in any attitude near the location of the
loop system and means combining the signals from the loops for
providing the output signal; and
a control unit receiving the output signal from the loop system for
transmitting a signal operating the deterrent, the control unit
having a detecting system, the detecting system having two
detecting circuits each receiving the output signal from the loop
system and each having a local oscillator arranged to oscillate at
a frequency displaced from that of a different one of the token
oscillation frequencies in the loop system output signal, means
mixing the loop system output signal with the local oscillator
frequency for forming beat frequency pulses, and a gate arranged to
count the beat frequency pulses during at least part of a signal
from a clock for passing a signal having a 0 or 1 state dependent
upon the counting of a predetermined number of beat pulses during
the clock signal, the control unit also having a clock for
providing the clock signal to each gate and means responsive to the
state of the signal from each gate for providing the signal
operating the deterrent.
22. A system as in claim 21 wherein the means combining the signals
from the loops in the loop system comprise means for oppositely
shifting the phase of the signal picked up by each loop and means
adding each of the oppositely phase-shifted signals for providing
the output signals.
Description
BACKGROUND OF THE INVENTION
This invention relates to security systems for controlling the
admission of authorised and unauthorised persons to particular
areas and to equipment for use with such systems.
SUMMARY OF THE INVENTION
According to one aspect of the present invention a security system
includes at least one portable token capable of transmitting
oscillations at a predetermined frequency, a control unit arranged
to detect whether oscillations at the predetermined frequency are
being picked up at a certain location and means for operating a
deterrent by the control unit. The system is preferably a radio
system.
If, for example, there are a number of security areas and some
persons are permitted to go in all of them whereas others are only
permitted to go into some of them, the persons can have tokens with
different transmitters dependent on their degree of authority and a
pick-up and radio receiver associated with a particular area and
forming part of the control unit can be arranged to control a door
or opening constituting the deterrent to restrict entry to persons
having transmitters transmitting one frequency, or any one of a
number of particular frequencies or those frequencies so modulated
by other frequencies. The transmitters can be arranged to be
operated continuously so that provided a person has the transmitter
on his person he can have access to the area without having to take
any action on entry. The transmitters could operate from batteries
which are recharged or replaced from time to time and an extension
of the system can ensure that no person can take one of the
transmitters out of the establishment area, or bring one in.
The detector can be arranged to give an alarm, whether audible or
inaudible, that an unauthorised person is approaching the security
area or can be arranged to unlock or not unlock a gate or open or
not open a door controlling access to the area, or to take a
photograph of any unauthorised person, or any combination of these
or similar actions.
The system may include a sensor responsive to the presence of a
person to initiate a detection cycle in the control unit which will
set off an alarm or take other appropriate action if not cancelled
by receipt of one of the particular frequencies within the period
of the cycle which might be conveniently of the order of one
second.
The sensor could be a switch operated by the weight of someone
approaching or a photoelectric device or a passive or active
acoustic device, or a capacitive device, or a detector using
micro-waves or any other form of detector. In an application where
the deterrent is a door, the sensor can be constituted by a pick-up
of the transmitted signals from the token.
The pick up might use an inductive loop system for picking up
transmissions and this could be let into a wall and/or a ceiling in
a passage approaching the security area so that it would not matter
in what attitude the person was carrying his transmitter.
A single control unit can operate with a number of deterrents and a
number of tokens and a number of gates at a number of levels of
security.
The control unit includes means such as a local oscillator at a
frequency displayed from the predetermined frequencies for
providing a local reference signal and means responsive to the
picked up signal response and the local reference signal to produce
beat frequency pulses and a detector circuit arranged to
distinguish between beat frequencies above and below a certain
limit.
Preferably the control unit includes a counter and a low pass
filter for cutting off frequencies outside a permitted range from
the counter, the permitted range of frequencies including the beat
frequency. The beat frequency pulses can be counted over a known
time interval to see if the received frequency is close enough to
the local frequency.
In order to avoid `accepting` the `image` frequency, the local
frequency can be modulated by a few Hz for a fraction of the
detection cycle and not for the remainder of the cycle and beat
frequency cycles can be counted in one sense for the fraction of
the period and in the other sense for the remainder of the period.
The fraction will be preferably one half of the period.
The net count over the examination period will be dependent upon
the frequency at which the local oscillator is modulated for the
part period and so the detector of the count can distinguish
between the beat frequency derived from the correct transmitter
frequency and the same beat frequency derived from the image
frequency.
BRIEF DESCRIPTION OF THE DRAWING
The invention may be carried into practice in various ways and one
embodiment will now be described by way of example with reference
to the accompanying drawings in which:
FIG. 1 is a diagram illustrating the general principles of a
security system embodying the invention;
FIG. 2 is a diagram showing how different pick up loops in the
system can be inter-connected to avoid a null, and;
FIG. 3 is a block diagram of some of the components of the control
unit shown generally in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The system is for controlling access to different restricted spaces
and in the example being described, two doors 11 and 11' are shown
diagrammatically in relation to passage 13. The doors are normally
locked closed but are to be opened automatically to permit the
entry of any person having an appropriate token, but not to be
opened to others.
As a person approaches any door 11 a sensor 15 detects his presence
and sends a signal to a central control unit 16 which is rendered
active to examine whether the persons who operated the sensor 15 is
carrying a correct token 20. If so, a signal is supplied at 17 to
open the door 11 automatically, but if not, the door remains closed
and/or an alarm is given and/or a photograph of the person is
taken. A second photoelectric sensor (not shown) responsive to a
person going through the open doorway can cause an alarm to be
given if an unauthorised person passes through after an authorised
person before the door has closed again. The authorised person's
token will prevent the alarm being given as he goes through.
The signals are detected by an arrangement of inductive loops
indicated generally at 18 in the passage by which the door is
approached and signals picked up by the loop 18 are fed at 19 to
the control unit 16.
In this way if a user wearing the appropriate token approaches the
door, the door automatically opens for him without his having to
take any such action as using a key or presenting a coded disc to a
checking system; persons requiring access to the door 11 say would
have similar tokens generally at the same discrete frequencies but
if different persons were to be allowed access to the door 11' or
to both doors say, then these would have tokens generating at
different frequencies, or two tokens at the same frequency for the
door 11, one of which transmitted also at the frequency for the
door 11'.
The Sensor 15
The sensor may be a photo-electric device or a weight-mat or a door
handle switch or an infra-red device or indeed any device that can
detect the presence of a person in a particular position and it is
only required to supply an activating signal to the control
unit.
The Loop System 18
Many different loop systems are possible depending on the
particular application but the system being described uses a
three-loop system which avoids a null so that it does not matter in
what disposition the user is carrying his token.
As shown in FIG. 2, one inductive loop H is arranged to lie in a
horizontal plane, and may, for example, be embedded in the floor or
ceiling of the passage 13. A second inductive loop V is arranged to
lie in a vertical plane which is parallel to the path of people
entering the security area, and may, for example, be embedded in
the wall of the passage. The third inductive loop D lies in a plane
which is mutually perpendicular to the planes containing the loops
H and V, and may, for example, encircle the passage, so that a
person entering the security area will walk through the inductive
loop D.
The system is arranged, as hereinafter described, to admit, or
exclude, or give warning of, a person even when only one of the
loops is picking up a signal.
Because the loops have a low self-inductance, the signals produced
in them by a transmitter will be approximately in phase (or
anti-phase). The signal from the loop H passes to a phase shifting
circuit 24, which retards it by a phase angle of 45.degree., while
the signal from the loop V passes to a phase shifting circuit 25,
which advances it by a phase angle of approx. 45.degree.. These two
signals are, therefore, now in quadrature. They are then added
together by an adder circuit 26. Since the two input signals to the
adder are in quadrature, there will always be an output from the
adder, unless neither loop H nor loop V is producing a signal.
It is possible that there will be no signal from either of the
loops H and V in certain positions of the transmitter, since the
aerial of the transmitter is an elementary dipole. In such a case,
however, a signal will be picked up by the inductive loop D.
To avoid the possibility of a signal from loop D cancelling out, or
nulling, with the signal from the output of the adder 26, the
signal from loop D is added to the output of adder 26 by an adder
circuit 27, and subtracted from it by a subtractor circuit 28. In
this way it is ensured that if any of the loops H, V and D is
receiving a signal, it is impossible for the outputs of both adder
27 and subtractor 28 to be zero.
Two phase shifting circuits 29 and 31 and an adder circuits 32,
which function in the same way as the circuits 24, 25 and 26
respectively, ensure that an output is produced under all
conditions except when there is no output either from adder 27 or
from subtractor 28.
The Token
This is a multi-frequency oscillator in a sealed plastic cassette
to be tamper and shock proof and to be resistant to changes of
temperature and humidity. It is operated by a chargable battery
carrying a 20 hours charge. It is about the size of a small packet
of cigarettes.
A token is arranged to generate signals at 2 discrete frequencies
in the range 50 to 150 KHz and only opens a door 11 designed for
these two discrete frequencies. The frequencies need to be at least
20 Hz apart and this gives 5000 possible frequencies so that there
are 25,000,000 possible combinations of the two frequencies. The
token employs two crystal-controlled oscillators and a ferrite rod
aerial. It transmits continuously at the two frequencies, being
re-charged at night when not being used. Alternatively it can be a
passive generator which is excited into oscillation when it
approaches the door by a signal generated in the loop system.
The Control Unit 16
This is in a central consule and receives signals over lines 12
from the sensors 15 disposed throughout the plant in relation to
all the doors 11, and from their associated loop system 18, and
also controls the transmission of unlocking or alarm signals over
lines 17 to the associated doors.
There is a display as indicated at 31 for each of the doors 11, 11'
etc., indicating whether a door has been approached by a person and
whether or not it accepted or rejected the person. The unit
includes a battery charger and a number of lockable sockets
indicated generally at 32, into each of which one of the tokens can
be inserted at night for recharging the batteries. There is also a
check that all tokens have been returned and have not for example
been taken home accidentally by the users. The unit may keep a
record of the times at which tokens were withdrawn and the times at
which they were replaced to keep a record of the hours during which
persons were on the premises.
The control unit can provide on a display board a single visible
display of the condition of the various doors and of the presence
or otherwise of the various tokens and there may also be one or
more remote displays controlled from the unit 16.
An additional feature is an exit loop detector at the exits from
the premises which gives a signal if any person tries to leave the
premises whilst still carrying his token.
The unit 16 may have a pre-programmed timer so that at different
times of the day different persons have access to the premises. For
example cleaners may be allowed in at certain hours when it is
known that the equipment to be protected is separately locked or
guarded.
Detecting System
The detecting system used in the control unit 16 for each of the
doors 11 will now be described in more detail with reference to
FIG. 3.
The signals from a pick-up coil 18 are received at 19 by a radio
frequency amplifier 35 whose output is fed to two different
detecting circuits, one for each of the two discrete frequencies to
which that door 11 is to be responsive. Thus the output from the
amplifier 35 is fed in parallel to two mixers 36, and 36' each of
which also receives an input from a local oscillator 37 or 37'.
Since tht two detector circuits operate in precisely the same way
except for the particular frequency to which they are responsive,
only one of the detectors will be described in detail.
Assuming that the detector to be described is to detect a frequency
of 90,040 Hz then the associated local oscillator 37 will be
arranged to oscillate at a frequency displaced from that frequency
by a few Hz, for example 90,039 Hz and the output from the mixer 36
if the correct frequency is being received at 19 will be a beat
frequency of 1 Hz, which is fed to a unit 38 including a low pass
filter cutting off at 20 Hz and a pulse shaper. The pulses from 38
are fed in parallel to an up gate 39 and a down gate 41 controlled
from a square wave clock generator 42 with a cyclic period of 400
milliseconds, and also from signals received at 43 from the sensor
15 associated with the particular door 11.
A sensor's signal at 43 renders the gates 39 and 41 active to count
beat pulses from the unit 38, each for the duration of respective
200 milliseconds halves of the square wave from the clock generator
42. This is achieved by an inverter 60 in the connection from the
generator 42 to the down gate 41. The clock generator is free
running and does not need to be synchronized with the sensor
signal.
The local oscillator 37 is also controlled from the clock generator
42 in such a way that the local frequency from oscillator 37 is
reduced by 9 Hz during one up part of the detecting cycle which
detecting cycle is established by the two, 200 millisecond halves
of the square wave from the clock generator 42.
Thus for the up part of the cycle, lasting 200 milliseconds, a
received frequency of 90,040 Hz would produce 2 beat pulses, and
for a second, down part it would produce 0 beat pulses. If the gate
39, the up gate, counts up to 4 pulses while it is active, it
passes a 1 signal to an accept gate 44, but if the count is 5 or
more, it passes an 0 signal. The gate 41, the down gate, passes a 1
signal to a non-accept gate, 45 if it counts 0 - 2 pulses while it
-- the down gate -- is active, and passes an 0 signal if it counts
more than 2 pulses. The gates 44 and 45 pass logic signals to a
final counter 52.
The final counter 52 is switched on at 50 by a pulse from a unit 58
driven the signals from the by clock 42 and triggered by the sensor
43 so that the counting of counter 52 coincides with the signal
from the gates 39 and 41.
Beat pulses at a frequency above 20 per second will be filtered out
at 38, and therefore incoming frequencies above 90,045 Hz and below
90,010 will not provide the appropriate beat pulses at 39 and 41,
and at the final counter.
Incoming frequencies in the range 90,010 to 90,025 and in
particular the image frequency 90020 will not product a net count
of 0 - 2 in the down gate 41, and so the receiver can be sensitive
to the narrow band 90,025 to 90,045.
It will be appreciated that slight variation of the local
oscillator frequency or the token oscillator frequency within their
tolerance of 5 Hz does not affect this test for the image
frequency. Also, white noise from a wide band noise generator would
not pass the filter and would produce a net count of 0 at 52. The
count system prevents an accept signal due to a 100%
amplitude-modulation of sub-sonic frequency.
The final outputs from the counter 52 for both discrete frequencies
are examined in a logic unit 54 which is capable of passing an
`accept` signal at 55 to unlock the door 11 over the line 17.
There may have been no accept signal because the final count was
greater than 4 possibly due to extraneous pulses, or because the
incoming frequency was too far displaced from the local oscillator
frequency giving a count of `0`; accordingly it is arranged that a
`second look` is automatically made.
Thus if no accept signal appears at 55, a second look signal is fed
from the logic unit 54 to the final counter at 61 and when the next
signal appears at 50 after a delay of 0.5 seconds -- sufficient to
complete the detecting cycle -- the unit is reset at 57 and a
further detecting cycle is performed to see if this time the
correct number of net beat pulses is counted.
In this way a false reject signal or alarm signal will not be given
merely because of some extraneous cause which does not repeat
itself during the next sampling period.
In an application in a prison, warders could carry the tokens and
could have a choice of two frequencies on one token, either of
which would open the door, but one of which would also sound an
alarm.
* * * * *