U.S. patent number RE29,183 [Application Number 05/498,638] was granted by the patent office on 1977-04-12 for telephone range expander.
Invention is credited to Gene Greneker, III.
United States Patent |
RE29,183 |
Greneker, III |
April 12, 1977 |
Telephone range expander
Abstract
An extension telephone is coupled to a telephone line through a
control unit which receives and forwards by radio incoming calls
and is fully controlled from the extension unit for outgoing calls.
Incoming calls ring the remote mobile unit which is then coupled
for conversation to the line through a control unit actuated from
the extension unit. The mobile unit transmits actuation and dialing
signals to the control unit for outgoing calls from the mobile unit
in response to successively transmitted tone modulations to dial
any party on the telephone line and thereupon connects the mobile
microphone and receiver directly to the line.
Inventors: |
Greneker, III; Gene (Decatur,
GA) |
Family
ID: |
27052896 |
Appl.
No.: |
05/498,638 |
Filed: |
August 19, 1974 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
884505 |
Dec 12, 1969 |
03721771 |
Mar 20, 1973 |
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Current U.S.
Class: |
455/554.2;
379/387.01 |
Current CPC
Class: |
H04M
1/72505 (20130101); H04M 19/04 (20130101) |
Current International
Class: |
H04M
1/725 (20060101); H04M 19/00 (20060101); H04M
1/72 (20060101); H04M 19/04 (20060101); H04M
003/06 () |
Field of
Search: |
;179/41A ;325/55,64 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Robinson; Thomas A.
Attorney, Agent or Firm: Powell; B. J.
Claims
I claim:
1. Extension telephone apparatus for connecting a mobile telephone
to a telephone line at a subscriber's station, comprising:
mobile transmitter and receiver means including a means for
transmitting first and second tones alternatively and for
connecting transmitter and receiver elements in the talk mode,
control unit means at said station for receiving said transmitted
tones and transmitting to the mobile receiver signals on said
line,
filter switch means operable in response to receipt of said first
tone,
stepping switch means response to operation of said filter switch
means, having first, second and third operated positions,
means connected to said first position for applying to said line
dialing pulses according to intervals during which said second tone
is received,
means connected to said second position for energizing transmitting
means in said control unit and for connecting said line to last
said transmitter means,
means connected to said third position for resetting said stepping
switch means to nonoperated position, and
means in said control unit for generating ringing signals for
transmission to said mobile means in response to ringing signals on
said line.
2. Apparatus according to claim 1 said transmitter and receiver
means comprising:
means in said extension unit for selectively generating for
transmission a first frequency switching mode modulation signal and
a second frequency dialing mode modulation signal,
means in said extension unit for applying voice mode acoustic
signals as a modulating signal when neither the switching mode nor
the dialing mode signal is transmitted,
switching means in said extension unit for selecting either of said
generated signals or said voice signal in accordance with said
modes, and
means in said fixed station for detecting each occurrence of said
switching signals and for thereupon completing a corresponding
coupling to a telephone line, according to one of said modes.
3. In a system according to claim 2, said detecting means
comprising tone selective filter means for operating a switch
whenever a tone corresponding to said switching signal is
generated, a switch operably connected to said tone selective
filter means and operatively connected to further means in said
fixed station for controlling the interconnection of the
transmitter and receiver therein with said line for conveying
signals to and from the extension unit according to the selected
mode.
4. In a system according to claim 2, said detecting means including
switch means responsive to said switching signal for connecting
said fixed station transmitting and receiving means to said line in
accordance with mode selected at the extension unit.
5. In a system according to claim 2, means at said fixed station
for switching according to said modes comprising a stepping switch
having a normal position and a plurality of operated positions, one
said operated position being connected to enable circuit means for
pulsing said line according to said dialing mode signal and another
operated position being connected to couple fixed station
transmitter and receiver means to said line whereby said extension
unit is coupled to said line in a talk mode.
6. In a system according to claim 5, relay means connected
responsively to said fixed station receiver when said stepping
switch is on said one position, said relay having closed contacts
connected across said line when actuated by a ringing signal.
7. In a system according to claim 5, means at said fixed station to
disconnect fixed station transmitter from its battery during
dialing mode, when said stepping switch steps to the dial circuit
position.
8. Extension telephone apparatus for receiving and initiating calls
from a subscriber's station under control of a mobile telephone
unit, comprising:
mobile unit means for transmitting to and receiving from said
station voice and ring signals,
mobile unit tone generator means for alternatively producing first
and second tones,
means for applying said tones when produced to cause transmission
thereof to said station,
means in said mobile unit for interrupting one of said tones when
produced according to a dialing code,
mobile unit means for operating said tone generator to produce at
the operator's election said first or said second tone and for
disabling the tone generator during desired intervals of telephone
reception from said station,
subscriber's station means for receiving transmission from said
mobile unit,
telephone line control means responsive to receipt of said first
tone for coupling the receiving means to a telephone line during a
first interval,
said coupling means including means for coupling a dialing code
signal to the line and for coupling said line to station
transmitting means during a second interval,
station transmitting means for conveying signals received to said
mobile unit, and
means for coupling said line to said station transmitting means
during a third interval in response to receipt of two pulses of
said first tone,
said control means including a stepping switch connected to couple
the line to the station transmitter in one position of advancement
and to couple outgoing ringing signals to the line in another
position of advancement, and including a third position having
automatic resetting means coupled therethrough.
9. Apparatus according to claim 8 said station including filter
switch means operative only when said first tone is received to
advance said stepping switch by one position each time the tone is
received.
10. Apparatus according to claim 8 operative when said stepping
switch is not advanced to couple incoming ringing signals to said
station transmitter. .Iadd.11. Extension telephone apparatus for
remotely using a telephone line at a subscriber's station
comprising:
a mobile unit including:
mobile transmitter means,
mobile receiver means;
tone means for alternatively generating a first tone and a second
tone; and
selector means for selectively connecting said tone means to said
mobile transmitter means to cause said tones generated by said tone
means to be transmitted through said mobile transmitter means;
and,
a control unit at the subscriber's station including:
control transmitter means for transmitting to said mobile receiver
means signals on said telephone line;
control receiver means for receiving said first and second tones
transmitted by said mobile transmitter means;
filter switch means connected to said control receiver means and
operable in response to receipt of said first tone;
stepping switch means responsive to operation of said filter switch
means having normal, first and second operated positions;
ringing circuit means operatively associated with said normal
position of said stepping switch means and said control transmitter
means for generating ringing signals in response to ringing signals
on the telephone line and causing said control transmitter means to
transmit said generated ringing signals;
dialing means operatively associated with said first position of
said stepping switch means for applying dialing pulses to the
telephone line in response to receipt of said second tone by said
control receiver; and
talk means operatively associated with said second position of said
stepping switch means for connecting said control transmitter means
to the telephone line and energizing said control transmitter
means.
.Iaddend..Iadd.12. The apparatus of claim 11 wherein said ringing
circuit means includes:
light emitting means electrically connected to the telephone line
constructed and arranged to be illuminated in response to ringing
signals on the telephone line; and,
a photocell optically associated with said light emitting means
constructed and arranged to cause an electrical signal output to be
generated in response to illumination of said light emitting means,
the ringing signals on the telephone line being electrically
isolated from the electrical signal output of said photocell.
.Iaddend. .Iadd.13. The apparatus of claim 12 wherein said light
emitting means includes a neon bulb. .Iaddend..Iadd.14. The
apparatus of claim 13 wherein said ringing circuit means further
includes:
oscillator means for generating an oscillating output signal when
energized, said output of said oscillator means operatively
connected to said control transmitter means; and
ringing switch means operatively connected to the electrical signal
output of said photocell, said oscillating means and said
transmitter means to cause said oscillator means to generate the
oscillating output signal and said control transmitter means to
transmit said oscillating output signal to said mobile unit when
said neon bulb is illuminated. .Iaddend..Iadd.15. The apparatus of
claim 11 wherein said selector means in said mobile unit is
effective to cause said filter switch means in said control unit to
operate said stepping switch means in said control unit and
selectively cause said stepping switch means to assume said normal,
first or second positions. .Iaddend..Iadd.16. The apparatus of
claim 15 wherein said stepping switch means is sequentially stepped
between said normal, first and second positions with said switch
means stepping to the next of said operated positions in response
to each receipt of said first tone by said filter switch means.
.Iaddend.
Description
In seeking means to extend the range of calling at a local
telephone, a number of prior arrangements have been devised to
permit mobile operation through a connection to land lines. Typical
of these are U.S. Pat. Nos. 3,009,149, 3,087,998, 3,124,657, and
3,193,623. Each of the proposed systems has certain disadvantages,
usually lacking the complete control of the subscriber's terminal
by the mobile unit, which in most such systems is subordinate to a
terminal unit where line connection is made or has other
objectionable features such as excessive band width requirements
for a radio link between the mobile unit and terminal or land line
coupler.
The first mentioned patent is basically a control system for
selecting which of a number of mobile units at a station is to be
called by the line terminal station, rather than an extender of the
range of operation desired for a particular subscriber's telephone.
The second patent is somewhat similar to the first except that the
unit acquires telephone lines and supplies digital dialing
information through the transmission of a combination of
simultaneous tones, while the third patent operates by radio to
couple a remote transmitter to a telephone line, but transmission
to the user is by radio loudspeaker signal which may be
unintelligible in a high ambient noise location. The dialing cycle
in this unit is accomplished by interrupting the radio frequency
signal and is accordingly subject to frequent error as such a
signal has no distinct recognizable coding and may be interrupted
or lost momentarily. Additionally, line acquisition depends on
constant presence of R.F. signal; thus, a fade or interference
signal may lose telephone line acquisition, thus losing the party
instead of a mere syllable. The final patent mentioned is a duplex
transmitter and receiver for a mobile unit employing a 10 kHz
continuous modulation to acquire and hold connection through the
fixed station to the telephone line. While this system operates to
call mobile units and to permit calls from the mobile unit, both
for ringing and talking, it has a number of disadvantages,
including the fact that if the signal containing the 10 kHz. line
acquisition tone fades, after a brief delay, line acquisition will
be lost; thus the conversation will be involuntarily terminated.
Additionally disadvantageous is the requirement of excessive band
width when in the talk mode and excessive power for a mobile unit,
due to the fact that the receiver, transmitter, and tone circuits
must operate simultaneously while the unit is in operation.
It is an object of this invention to provide a remote mobile unit
in which a subscriber's control of a telephone line is the same as
in an ordinary connected telephone, but in which the line coupling
control is completely effective from the mobile unit.
Another object of the invention is to provide improved switching
arrangements for control of access to the line for dialing and talk
modes and for resetting by radio from a small mobile unit carried
by the user.
A further object of the invention is to provide a remote telephone
coupler controllable by the user with minimum power consumption and
an improved reliability of caling and receiving calls in a dial
system.
A still further object of the invention is to provide user
controlled apparatus for connecting a mobile unit to a subscriber's
telephone terminal connection to a telephone line by short wave
radio.
These and other objects of the invention will be perceived as the
description proceeds in relation to the drawings in which:
FIG. 1 is a block diagram of a system according to this
invention;
FIG. 2 is a block diagram of a user's "walkie-talkie" unit showing
modification for extension phone use;
FIG. 3 is a block diagram of transmitter, receiver and control
units compatible with apparatus of FIG. 2, including schematic
circuitry in part;
FIG. 3A is a schematic diagram of a dial relay driver;
FIG. 3B is a schematic diagram of a tone decoder;
FIG. 3C is a schematic diagram of an A.V.C. circuit suitable for
use in an audio input circuit to the transmitter of FIG. 3; and
FIG. 3D is a schematic diagram showing connections for the control
unit of FIG. 3 to a line through a telephone company-supplied
coupler.
A subscriber's desk or wall telephone is replaced by or
supplemented by a terminal including a transmitter, receiver and
control unit connected directly to the line in the same way as a
conventional user's phone, or is connected to a line coupler
supplied by the telephone company which is in turn connected to the
line. This control unit operates a transmitter for incoming call
ringing and talk modes and is operated to switch to and from both
ring and talk modes by received mobile unit control pulsing for
both incoming and outgoing calls, the linkage for transmitting and
receiving between mobile and terminal units being by radio or other
variable path medium. A complete control of the terminal unit from
the mobile unit for outgoing calls and for incoming calls after
ringing is provided by a pair of generated tones, one to perform
switching, and the other to effect transmission of dialing pulses
over the line under the control of the mobile conventional dial
signal interrupter. Repeated sequential transmissions of the first
tone steps a switching mechanism in the terminal control unit to
connect and disconnect the terminal transmitter and receiver for
the talk mode and to make and break connections for outgoing call
line acquisition. As a preferred embodiment the transmisson between
mobile and terminal units is by conventional short wave radio
apparatus operating in the Citizen's Band employing no more than
200,000 Hz., total receiver transmission separation, while sending
and receiving simultaneously. Total band width of either
transmitter is limited to the highest voice frequency used, in this
case 3.5 kHz. Only one of the generated tones is used at any one
time, neither being required when the talk mode connections are
effected. A return-to-standby is effected automatically upon
failure to complete the enabling connections and upon completion of
a call or at a predetermined time for cancellation.
Referring now to FIG. 1 there is shown in block diagram an
extension system wherein connection to a telephone line 10 is
effected through a telephone control unit 11 powered by a DC source
such as 12 volts supplied from an AC line. Control unit 11 is
effective to transmit ringing pulses and telephone messages by
means of a transmission medium coupler 15, illustratively a radio
antenna for broadcasting in the immediate area a modulated radio
frequency signal such as the Citizen's Band frequency near 27 MHz.
Control unit 11 further has a signal-receiving coupler such as a
radio receiver having antenna 14. When propagation between the
control unit and the user's hand-held unit is via radio, as
illustrated, conventional transmitter 15 is connected between
antenna 13 and the control unit 11, and serves to transform audio
output on line 16 to a modulated radio frequency output at antenna
13. As will be further described hereinafter the energization of
transmitter 15 is effective intermittently, according to the signal
to be transmitted, by selective energization of transmitter 15 via
line 17 from the control unit. Receiving coupler 14, when
transmission is by radio, includes a conventional radio receiver 18
comprising the usual tuning circuit and demodulator to provide an
output by way of leads 19 in manner to be later described.
A portable telephone extension is shown generally at 111 which
comprises a suitable package for hand holding, or for suspending by
a shoulder strap, or the like. Unit 111 consists essentially of a
mode switch 121, a dialing switch 130 and a tone generator 112
producing two tones alternatively for actuating dialing functions
by way of control unit 11, and switching mechanisms to enable the
extension phone to control unit 11, which then activates the
extension phone so that the subscriber's station is connected to
telephone line 10.
This unit comprises a "walky-talky" type radio to which is added
circuitry generally illustrated in FIG. 2, including mode switch
121 having three banks of three positions each shown at 121A, 121B,
and 121C. When switch 121 is on position 1 a direct connection is
made between the user's microphone 110 at line 117 and the audio
input to the walky-talky transmitter shown at line 116. In this
position the user talks directly with anyone connected to the line
through control unit 11. Antenna unit 113 serves both as a
transmitting and receiving antenna cooperating with antennae 13 and
14.
Mode switch 121 is manually operable by the user to connect his
transmitter and receiver through unit 11 to line 10, to control the
tone generator, and to switch functions in unit 11. Tone generator
112 produces two distinct tones as switch 121 is operated to
positions 2 and 3 to dial a number and switch the control unit to
the talk mode. On position 2 a first frequency such as 400 Hz. is
generated and transmitted for switching functions in unit 11 and on
position 3 a second frequency such as 350 Hz. is generated and
transmitted to unit 11, to operate therein a dialing relay to
provide a telephone line dialing pulse when interrupted once for
each dial position passed in one direction of dial movement as the
operator dials his desired party at hand-held unit 111. When a line
has been signalled, mode switch 121 is again operated to produce
the first frequency a second time for switching to connect power to
transmitter 15 for conveying the receiving telephone line voice
signals via transmitter 15, antenna 13, antenna 113 and demodulator
118, producing an audio signal in receiver 119. When the
conversation is completed switch 121 is again operated to clear the
line by generation of the first tone a third time, for a switching,
clearing action in unit 11.
Initiation of a telephone call from the extension phone occurs as
the operator advances switch 121 to position 2 thereby connecting a
DC voltage such as 9 volts on supply line 122 via load resistor 123
to the collector of a twin-T transistor oscillator circuit having a
base bias resistance 124, transistor 125, biasing
resistor/capacitor network 126, and frequency tuning capacitor
network 127 connected to the wiper of switch 121C.
In position 2 a variable resistor shown at T.sub.1 is set to
produce, in cooperation with the capacitors 127, a first frequency
of oscillation which is passed by line 128 to switch bank 121A and
thence to the audio input 116 for the transmitter. Whenever switch
121 is on either position 2 or 3 the power is supplied to 125 via
123. After a brief dwell on position 2 the switch 121 is advanced
to position 3, and a second tone is generated under control of
T.sub.2. The second tone is passed by the transmitter to receiver
18 and operates to pulse telephone line 10. Since conventional
telephone line dialing is accomplished by a line short being
interrupted once for each dial position passed over, and translated
at the central switching office into a line selection, a like
function is here provided. The second tone, controlled at T.sub.2,
provides a line shorting signal that is pulsed off by interrupting
the current flowing to a ground return circuit connected to the
oscillator emitter by way of line 129 and normally closed dial
switch 130. The walkie-talkie unit carries a a dial mechanism like
that of the usual desk telephone, not shown. This dial mechanism
includes a switch actuator illustrated in FIG. 2 at 131 which
cooperates with a normally closed switch 130 in a conventional
manner to interrupt the dial signal each time the dial actuator 131
passes one of the dialing positions, causing switch 130 to open and
form a dial pulse. The dial tone signal being transmitted from unit
111 to unit 11 causes a switch to close across line 10. Thus, when
the dial is moved to the "0" position and allowed to return to the
rest position there will be ten interruptions of the ground return
circuit to the emitter of transistor oscillator 125. This
effectively provides 10 interruptions of the switch shorting line
10, as in normal telephone dialing.
Referring now to FIGS. 3, 3A, 3B, and 3C, control unit 11 will be
described for one embodiment of the invention in which the control
unit is connected directly to telephone line 10. In a second
embodiment of the invention a conventional
telephone-company-supplied coupler unit is employed with only
slight changes in the circuitry of FIG. 3, this being shown in FIG.
3D. When direct connection is made to the line a line switch or
relay 20 is utilized to make connection between line 10 and the
ringing circuit or the talking circuit in accordance with operation
of the user's unit. A relay coil 21 operates a pair of switch arms
connected to points 22 and to the line 10. A pair of ringing
circuit connections are made at points 23 of switch 20 which are
normally closed except in the talk mode. Lines c and d connect line
10 to the transmitter and receiver in the talk mode via pair of
contacts 24, normally open and arranged to be closed when relay 20
is operated. In the unactuated position of relay 20 lines a and b
connect to points 23 and thence through points 22 to the line,
while lines c and d connect to points 24 and thence to the line.
Relay 20 is operated by voltage applied between lines e and f in
accordance with the position of a stepping relay later to be
described. Points A, B, C, D, E and F are points of disconnection
of relay 20 and of connection to the previously mentioned line
coupler. The line coupler is supplied by the telephone company when
the regulations of the company require the control unit 11 being
connected at points G and H to introduce ringing pulses to unit 11,
then supplying the actuating pulses for initiating coupler output
to the line.
For an incoming call a ringing pulse arriving on line 10 is passed
through points A and B of lines a and b. Since lines a and b extend
to normally open switch 39 of dial relay driver 30 no effect is
produced thereby within the control unit. However, the line sees a
load through the normally closed contacts of switch 39, lines
extending to a ring initiator circuit passing in one case from
point B through a disconnect point I to a ring control circuit and
through point A and the normally closed pair of contacts on switch
39 thence through disconnect point K to the other terminal of the
ring actuator circuit to produce a further ring signal for
transmission to the receiver unit. Loading of line 10 during the
stand-by mode of unit 11 is undesirable because, ideally, line 10
should be presented no resistive load while idle, or while passing
the conventional AC pulse, used for ringing by the telephone
company, yet a circuit must be provided to recognize a ringing
pulse on line 10. These conditions are satisfied in the present
circuit 59 by use of a neon bulb which provides almost no resistive
load until fired, in this case by the ringing voltage. The neon
bulb is across line I-K, hence is operated by a line ring pulse,
and the light output is piped to a photocell to initiate a ring
signal transmission to unit 11 at points G and H inasmuch as the
telephone company-supplied coupler supplies a switch closure during
the ring cycle at G and H when connected as described, obviating
the need for the ringing signal generator shown. In this case
circuits are also broken at I and K, the normally closed switch
portion at 39 being left unconnected when the line coupler is
employed.
When relay 20 is operated and points 22 are connected to points 24
lines c and d are connected to a conventional hybrid telephone
transformer generally as indicated at 28 and as conventionally used
in a two line to four line telephone circuit termination, as in
present commercial practice. This hybrid transformer has a high
impedance output at line 25 extending to the automatic volume
control circuit 50 and to the transmitter 15 of the present
invention. Receiver 18 develops a balanced output in a
center-tapped-to-ground transformer 11' during all modes including
standby.
When the user operates switch 121 to position 2 to initiate a call,
a first tone is generated and transmitted and will be received and
demodulated in receiver 18 and the balanced audio output produced
in winding 12 of output transformer 11' will be conveyed by line 26
to the hybrid coil input windings 28, line 27 being the center tap
audio ground return. The output signal, however, does not produce
on line 10 any output for the reason that neither dial relay driver
30 nor relay 20 is energized and only non-resistive-terminated
lines a, b, I and K are connected to line 10.
At the same time, the demodulated signal from receiver 18 passes
through the top winding 12 of balanced output transformer 11',
extending through branch lines 27 and 31 to the dial relay driver
unit shown generally at 30, illustrated more specifically in FIG.
3A. An input transformer having input winding 32, connected at 27
and 31, has output winding 33 to an amplifier 34 suitably biased at
35 having undirectional output coupled to amplifier 36 and 36' to
operate a relay coil 38 in control of switch 39. Thus, when tone 2
is received at 18, relay switch 39 is operated to close a
connection across line 10 when relay 20 is not yet operated, and to
open the circuit between A and K at the normally closed contacts of
switch 39.
At the same time, the demodulated signal from receiver 18 is passed
from transformer 11' via winding 12, line 31 and branch lines 27'
and 31' to a frequency disciminating circuit shown in FIG. 3B at 40
having input via transformer 41 and output at lines 42 and 42'.
Input extends to amplifier 43 and transformer 44 in control of a
resonant reed circuit generally shown at 45, comprising an actuate
coil 46 and a moveable reed 47 which makes intermittent contact at
47' when the input frequency corresponds to the reed frequency so
that a resonant condition exists. This provides actuation voltage
for relay coil 48, closing normally open contacts 49. Rapid
response is achieved by use of amplifying means at 48', which may
be biased into conduction by voltage applied at 47', preferably
smoothed by a suitable high value of capacitance to maintain relay
coil 48 energized whenever the resonant condition is satisfied.
Circuit 40 as illustrated operates whenever tone controlled by
T.sub.1 is generated at the user's unit 111 and impressed on line
31, closing switch 49 and connecting line 42 to line 42' which
connects to power lead 54, thus applying power to lead 42 for
actuation of the stepping switch to connect line 10 to lines c and
d and to actuate the transmitter in the talk mode.
When receiver 18 obtains demodulated output on lines 26 and 31
according to any product generated at unit 111 hybrid coil 26 would
pass this product to lines c and d which would pass to line 10 if
actuation of a stepping switch to position 2 had occurred to
provide operation of relay 20. In the ringing mode this has not yet
occurred. The telephone line output voltage appears at the output
of the hybrid coil 28 and would return a strong signal to unit 111
through transmitter 15 via line 25 but is not effective since 15 is
not energized. Automatic volume control circuit 50, shown in more
detail in FIG. 3C, operates to produce a regulated audio ouptut at
line 51. This circuit standardizes the audio input for the
transmitter but is not described in detail since it is conventional
and may be varied according to operating characteristics which may
be desired.
When an incoming ring signal arrives by line 10 it is necessary to
convey this signal by way of transmitter 15 to unit 111 to produce
a ringing signal at receiver earphones 119. An incoming ring signal
appearing at points A and B is passed by normally closed contacts
of switch 39 and produces an output signal by operation of relay Re
5 and oscillator 53 to line 52 connected to audio output line 51.
This ringing signal is produced by a conventional oscillator 53 as
switch 55 closes on operation of Re 5 to apply power from line 54
to oscillator 53, a conventional oscillator tuned to a frequency
suitable for operating the desired buzzing signal at speaker 119 of
unit 111. This oscillator includes a load resistor 56 connected
through switch 55 to power lead 54 whenever Re 5 is operated. A
suitable transistor oscillator shown generally at 57 has a
resistance-capacitance network for generating a signal in the audio
range connected to output lead 52. The neon bulb converts the AC
ringing signal to light and photocell 58' reconverts the light
impulses back into an analog electrical signal. As light of the
neon bulb strikes the photocell 58' its resistance lowers, allowing
current to pass to the base of transistor-amplifier 58, driving it
to conduction to power Re 5 to operate ring circuit 59. There is
thus provided means of ringing extension phone 111 and for dialing
a number at phone 111 to effect the closing of switch 49 whenever
the first tone is generated under the control of T.sub.1 when
switch 121 is on position 2. When switch 121 is advanced to
position 3 a different tone under the control of T.sub.2 is
generated which is not of a frequency accepted by 45 to close
switch 49. However, a brief or momentary operation of switch 49 is
sufficient to actuate step-switching of the control unit one step
each time it occurs. Such an operation is effected each time manual
switch 121 is advanced to position 2, or passes position 2 in
returning to position 1 for connecting user's microphone to his
transmitter. As the user desires to commence dialing he advances
switch 121 to position 3 and produces dialing pulses of the second
frequency by operation of dial 131. Upon completion of dialing he
returns switch 121 to position 1 contacting position 2 in passing,
and his microphone is again connected to line 116 for the talk
mode. The first tone is again produced as he passes position 2 to
provide a second connection of line 42 to the power lead 54. This
provides the desired second stepping pulse for a stepping switch in
control unit 11.
A stepping switch suitable for switching in control unit 11 is
shown at 60 in which advance coil 61 is connected to line 42 and to
system ground. Thus, closing switch 49 serves to step relay 60 one
step each time the first tone is received at circuit 40.
Alternatively, a push-button switch 62 may make connection between
the power lead 54 and line 42 for energizing coil 61 when it may be
desired to control unit 11 manually. Stepping relay 60 also has a
reset coil 63 arranged in conventional telephone stepping switch
manner to return switch 60 to its normal position after one or more
steps have been made. Reset coil 63 connects to system ground and
to an automatic reset delay relay later to be described. It also
connects to a push-button reset switch 65 for manual control in the
same manner as advance coil 61. Stepping relay 60 is provided with
two contact and wiper banks 66 and 67 having wipers connected to
power lead 54 and point E in line e to relay 20, and wherein wipers
may be in normally off position or in actuated positions 1, 2 or 3.
When advance coil 61 has been operated once, wiper 66 is on contact
1 of the upper bank to provide DC power supply to line 68 which
connects to energize dial driver 30 and to operate the dial light
85 to indicate that the user's unit has been placed in the dialing
mode. In position 1 power is not connected to transmitter 15 since
only the one first tone signal has been actuated at the unit 111 to
prepare the unit for dialing. However, a second pulse is received
on line 42 by reoperation of switch 49 and the upper and lower
wipers 66 and 67 advance to position 2 to provide power on line 69,
to operate indicator light 86, and to apply power through diode 80
to transmitter power input line 81, ground being applied by return
line 82. At the same time, wiper 67 contacts a ground connection to
supply ground return on line e for energization of relay 20 in
order to connect line 10 through hybrid transformer 28 and
automatic volume control 50 to provide talk mode audio input to the
transmitter 15. When the user at unit 111 wishes to terminate the
conversation or clear the line a third pulse is transmitted to 18
and passed to 40 then to line 42 by reoperation of switch 49. The
upper and lower wipers advance to switch position 3, to provide
power on line 63'. This power actuates reset coil 63 causing relay
60 to return, thus returning unit 11 to the stand-by mode.
At 70 is shown a conventional DC power supply such as 12 volts from
an AC line having a grounded output 71 to supply 12 volts to power
lead 54.
It is preferable to provide means independent of operation of unit
111 for resetting the control unit to its initial standby condition
whenever a series of events has been commenced in control unit 11
by operation of unit 111, and the signal is lost or otherwise fails
to complete a sequence of operation for a normal conversation. For
this purpose a pair of normally-open slow-closing relays are
provided with connections to lines 68 and 69. Lead 72 extends from
line 68, corresponding to the first position of stepping switch
actuation, to a coil 73 arranged to operate in a period of time
such as 30 seconds to close a set of contacts 74 for applying
voltage from line 68 to a line 64 connected to reset coil 63. Thus,
if a call is initiated and relay 60 is on position 1 for 30 seconds
the stepping relay will be returned to its normal off position.
Similarly, when a conversation has been commenced and has been in
progress for some time by virtue of wiper 66 being on contact 2
thus energizing line 69 and the transmitter via diode 80, lead 76
applies voltage from line 69 to coil 78 to close a pair of contacts
77 after a suitable time delay. This interval may be selected, for
example, at three minutes in order to reset the control unit if the
resetting operation has not been accomplished by way of a first
tone control pulse generated by a line-clearing operation of switch
121.
Employing the previously described circuitry it will be seen that
an incoming signal on line 10 passes through the normally closed
contacts of relay 20 and the normally closed contacts of dial relay
driver 30 to provide energization for relay Re 5 thus actuating the
ringing audio oscillator to supply a ringing signal to the
transmitter while the transmitter is energized by supply voltage on
line 54 through closed contacts of Re 5 via diode 83 and line 81.
The user of the remote unit, upon hearing this tone, then sets the
switch 121 forward to its position 2 a first time to step relay 60
one step. A second step is required. He may then return switch 121
to its normal position or pass it to position 3 and thence back to
position 1 whereby a second pulse is produced at switch 49 as the
first tone is produced a second time. This steps relay 60 to the
second position which connects the transmitter of unit 11 to line
10 and permits a normal conversation as long as switch banks 66 and
67 remain on position 2. Since the user has returned switch 121 to
its initial position his microphone is connected directly to the
audio input for his transmitter and a two-way talk mode channel to
line 10 is completed. Upon termination of the conversation he may
again actuate switch 121 to provide another pulse for stepping
relay 60 one more step which then resets to its off or home
position. If this third stepping by way of switch 49 does not occur
within the time limit imposed by slow-to-make contacts 77 a
resetting pulse is provided by the automatic reset delay and the
user's extension phone is disconnected from the line. Control unit
11 is then in a stand-by condition for further actuation either by
an incoming call on line 10, or by a call initiated by unit
111.
It will be seen that the user of unit 111 has complete control of
the control unit 11 and of the telephone line for received and
outgoing calls. A call initiated from the extension phone requires
first that the user move switch 121 to position 2 which generates
the first tone and this tone operates resonant reed circuit 40
closing switch 49. This immediately steps switch 60 to position 1
energizing line 68 and also operating dial driver relay 30 to
connect lines a and b at switch contacts 39 and to break the
ringing circuit through point K, thus preventing interference with
dialing by the user's unit. At the same time a resetting time
interval is commenced by the energizing coil 73. The duration of
the first tone is normally a few seconds or less before switch 121
is advanced to position 3 at which time the second tone is
generated to provide dialing pulses. Since circuit 40 is not
sensitive to this second frequency, and dial relay driver 30 is
enabled by application of power supply thereto via line 68 both the
first and the second tones are effective to close the switch 39
normally open contacts and open the circuit through K. This is the
condition for applying a line acquisition signal to line 10 and a
pulse will be repeated as often as the second tone is interrupted
by operation of switch 130. When a series of pulses corresponding
to each operation of actuator 131 has occurred switch 121 is then
returned to its initial position by way of position 2 to again
pulse circuit 40 closing switch 49 and stepping relay 60 to
position 2 to disconnect the outgoing ringing circuit from line 10
and connect the control unit in the talk mode through lines c and d
and the automatic volume control circuit 50 to provide an audio
input for transmitter 15 by way of line 51. The talk mode obviously
includes data as well as voice communications, substituting other
inputs and receivers.
As thus described means for controlling the ringing at the remote
unit is operative automatically, unless a sequence has already
commenced at the remote unit, and upon responding the user switches
his control unit line connector and his own mobile unit to the talk
mode by merely operating a switch through two steps and return. He
may terminate the talk mode by one more step of his local switch,
and thus return his unit to the receive mode for incoming calls. He
has complete control of the coupler to a telephone line by
positioning his mode switch or repeatedly operating it to position
2, and he may dial any outgoing call as though he were at a
normally operating subscriber's station on a telephone line. These
control operations are effected without the necessity of
transmitting any kind of a control signal during the talk mode,
since all switching is done before and after the talk mode. An
outgoing or incoming call may be initiated in a few seconds elapsed
time, not much different from the time for conventional subscriber
phone operation, and no other attendant is required. Band width on
the line is not changed and band width of transmission to the
control unit is only the normal audio band width within which
control tone modulations are nearly central, and minimum
requirements are imposed on the radio spectrum by many users in the
same locality. Interference between the user's transmitter and the
control unit transmitter is not of importance since each uses its
own narrow band of frequency, tuned as may be desired.
Land lines using a carrier wave modulated by voice or by digital or
analogue information may be substituted for the radio coupling
above described, and it is contemplated that a number of data
phones may be used from the same control unit by suitable tuning of
units to the respective carrier frequencies.
* * * * *