GB2166927A - Telephone control system - Google Patents

Abstract

An intercom system having direct access to an outside line comprises a central control unit which controls both connection of the outside line to each of a plurality of telephones and connection of the telephones to one another in the intercom mode. The system further comprises a respective local control unit positioned in close proximity to each telephone and including indicators in the form of a light-emitting diode and a buzzer for indicating an intercom call from another telephone and a push button which, when actuated, operates the indicators of another local control unit. Such a system can be used with any type of telephone, and is therefore very flexible and capable of installation at moderate cost. <IMAGE>

Description

SPECIFICATION Telephone control system This invention relates to a telephone control system, and is more particularly, but not exclusively, concerned with a telephone intercom control system having direct access to at least one outside line (hereinafter referred to as a telephone control system "of the type defined").

Known intercome systems having direct access to an outside line are relatively complex and therefore expensive. They require the use of specially adapted telephones interconnected by complex wiring, and are not particularly easy to use. Although it is possible for an outside call to be transferred from one telephone to anotherwithin the system, the transfer method is notfoolproof and there is a dangerthatthe outside call will be lost when putting the call on hold.

It is an object ofthe invention to provide a generally improved telephone control system.

According to the invention there is provided a telephone control system of the type defined comprising a central control unit including line connection means for connecting each of a plurality of telephones to an outside line and intercom connection means for connecting each of a pluralityoftelephonestoone another, and a respective local control unit which is preferably separate from, but intended to be placed in proximityto, each telephone to be connected to the system and includes indicating means for indicating an intercom call from another local control unit and actuating means which, when actuated, operates the indicating means of another local control unit. The indicating means may be an audible and/or a visual indicator, and the actuating mens may be one or more push-button switches.

In its preferred form, such a system possesses the advantage that it operates satisfactorily with almost any type of telephone intended for use with an outside line, whetherthe telephone is ofthe push-button or dial type. The central control unit and various local control units take care ofthe necessary control functions for enabling the individual telephones within the system to be connected to the outside line and for providing the intercom facility. Thus a system of greatflexibility can be provided at moderate cost.

Conveniently each local control unit is connected to the central control unit byway of a respective line jack unit which also includes terminals for connection of the associated telephone to the central control unit by way ofthe line jack unit In this case each line jack unit could be mounted on a wall,for example, at a convenientpositionclosetothelocation atwhichthe telephone is required.

In an advantageous development of the invention the central control unit includes holding means for automatically placing an incoming call on the outside line on hold when the intercom facility is in use, an indication ofthe incoming call preferably being provided on each local control unit by means of the indicating means. In this case the holding means may be arranged to release the incoming call from hold when the actuating means of one ofthe local control units is operated. Such an arrangement for placing an incoming call on hold is substantiallyfoolproof in use.

Furthermore full security from the outside line on an intercom call is provided.

The central control unit advantageously also in cludestransfer means for placing an incoming call received on one telephone on hold while the call is transferredto anothertelephone, the arrangement preferably being such that the call is placed on hold by actuation ofthe actuating means ofthe local control unit associated with the telephone receiving the call.

In this mode the caller on the one telephone may call the other telephone and converse with the person answering that telephone with full security from the outside line. Conveniently the person on the second telephone may then obtain the incoming call by actuation ofthe actuating means on one of the local control units, the caller on the firsttelephonethen replacing his handset.

The invention also provides a telephone control system incorporating active line detection means for detecting when a telephone line is active comprising two comparators each having a respective input coupled to the incoming line and a respective input arranged to receive a reference voltage.

The invention further provides a telephone control system incorporating ring detection meansfordetect- ing a ringing signal on atelephone line comprising an optically coupled isolator having its light-emitting section coupled to the line and its light-detecting section arranged to provide a detection signal when a ringing signal is detected.

According to another aspect of the invention there is provided a telephone control system of the type defined in which intercom call and line hold and release are actuated by a single button. Such an arrangement avoids sequencing errors.

In orderthatthe invention may be more fully understood, a preferred form of system in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure lisa circuit diagram of a main control unit of the system; Figure 2 is a circuit diagram of one oftwo identical line jack units ofthe system; and Figure 3 is a circuit diagram of one of two identical desk pad units of the system.

In operation fourwire from an external jack are connected to the main control unit 1 of Figure 1 by means of a connector 2, the wires comprising first and second signal lines 3 and 4, a telephone earth line 5 and a ringing function line 6. Furthermore the main control unit 1 has its output 7 connected to the two line jack units 8, of which one is shown in Figure 2, by means of two 6-way connectors and associated leads, each connector being connected to a respective one of the output lines of each pair of output lines K1 to K6.

Thus one of each pair of output lines is associated with a respective one ofthetelephonesAand B. Each line jack unit has an input connector 9 comprising input lines 11 to 16 to which the output lines K1 to K6 of the main control unit 1 are respectively connected.

Furthermore the line jack unit 8 has a line jack socket 11 to which the associated telephone is connected in the conventional manner, and an output connector 10 having its output lines J1 to J3 connected by a lead to input lines M1 to M3 respectively of an input connector 12 of an associated desk pad unit 13. No connections are made to the unreferenced output lines of the socket 11 and connector 10.

The central control unit 1 is intended to be located in a suitable central position, whereas each line jack unit 8 is intended to be mounted on the wall close to the position in which the telephone is installed, in the manner of a conventional telephone jack socket.

Furthermore each desk pad unit is intended to be installed in the immediate vicinity ofthe telephone, being either loose on the desk orwall-fixed depending on whetherthetelephone is installed on a desk or a wall. The desk pad unit 13 is intended to be disposed close to the associated telephone and may, for example, incorporate a telephone note pad. Furthermorethe desk pad unit 13 incorporates a single push button 14, an indicator in the form of a light-emitting diode 15 and a buzzer 16.

The main control unit 1 has two modes, namely an intercom mode which offers intercom facilities between the two telephones and external line mode in which eithertelephone may be used as a normal telephone connected to the outside line. Switching between these two modes is accomplished by a 2-way line relay comprising a relay coil 28 and two relay switches 29 and 30, and a ring line relay comprising a relay coil 31 and a relay switch 32. The switches 29,30 and 32 are shown in the external telephone mode in Figure 1. In this modethe relay coils 28 and 31 are unenergised,the switches 29 and 30 connect the second external signal line 4to each telephone by way ofthe output lines K5, and the switch 32 connects the ringing function line 6 to each telephone by way of the output lines K3.The first external signal line 3 is connected to the output lines K2 and hence the telephones through a resistance 33.

When the handsetofeithertelephone is lifted, a currentflows through the resistance 33 and the resultant voltage is applied to respective inputs of opposite polarity of two comparators 34 and 35 by wayofa circuit point a. Reference voltages are applied to the other inputs ofthetwo comparators 34 and 35 from a voltage divider comprising four resistances 36 to 39. The currentflowthrough the resistance 33 produces voltages which vary aboutthe reference voltages provided by the voltage divider and which switch either the comparator 34 orthe comparator 35, depending on the direction of currentflow. This part of the circuittherefore forms a sensitive line detection system.

The outputs ofthe comparators 34 and 35 are supplied to respective diodes 40 and 41 which together serve as an OR gate, and the resultant output is supplied to a buffer comprising an AND gate 42 and a capacitance 43 in order to avoid line detection fluctuations during dialling.Theoutputofthegate42 is supplied to a further AND gate 44 and also to a diode 45 from where it is supplied to a drive amplifier 46 which drives the light-emitting diodes 15 ofthe desk pad units 13. A resistance 47 and a zener diode 48 serveto limitthe currentthrough the light-emitting diodes 15.

The system may be placed in intercom mode by operating either ofthe push buttons 14 on the desk pad units 13. Depression ofoneofthe push buttons 14 when the system is in the external line mode will cause a signal to be applied to the coil 25 of a buzzer relay so as to close the associated relay switch 26 and clock the input CP of a D-type fl i p-flop 49to settheflip-flop 49, whereas, if either button 14 is subsequently pressed, theflip-flop 49 will be reset. The output Q ofthe flip-fiop 49 is fed through a drive amplifier 66 to the coil 28 ofthe line relay and also to the coil 31 ofthe ring line relay.When the coils 28 and 31 are energised the switches 29,30 and 32 are placed in the opposite positions to those shown in Figure 1, and this causes each telephone to be disconnected from the external signal line 4 and from the ringing function line 6.

Simultaneouslythe output lines K5 are connected by the switches 29 and 30to the coils 67 and 68 oftwo relayswhichtogetherwith a capacitance 69 form a transmission bridge. This switches each telephone from the exchange line to the intercom circuit which is powered from a 1 6V supplythrough the transmission bridge. The relays each serve to detect whether a respective one ofthetelephone handsets is off-hook.

When both handsets are replace,theswitches70and 71 associated with the two relays simultaneously supply signals two the inputs of an AND gate 72, and this presents a pulse to the clea r in put CD of the flip-flop 49 by way ofthe RC network constituted by the capacitance 73 and the resistance 74, thus clearing the - flip-flop 49.Asimilarsequence of operations occurs after power-up in orderto resetthe system.

The signals produced bythe switches 70 and 71 are also supplied to diodes 75 and 76 which together act as an OR gate to produce an output signal when one or both ofthetelephone handsets is on-hook. This output signal is applied to one input of an AND gate 77 to the other in put of which the output oftheflip4lop 49 is applied.Furthermore the output ofthe AND gate 77 is supplied by way of a diode 78 to one input of a NAND gate 53 to the other input of which the output of theflip-flop49 is also applied.ACMOS oscillator comprising NAND gates 55to 57, a capacitance 58 and two resistances 59 and 60 is connected to the output of the gate 53 by way of a diode 54, and the oscillator provides a signal to drive the buzzers 16 of the desk pad units 13 when the push button 14 on one ofthe desk pad units 13 is depressed and one or both ofthe handsets is off-hook.

Switching of the switch 32 ofthe ringing function relay when the system is placed in the intercom mode also serves to switch into circuit a ring detect circuit comprising a resistance 88, a diode 89 and the light-emitting diode 90 of an opto-coupler. When an incoming ringing signal is received on the external line, the ringing current flows through the resistance 88 and the light-emitting diode 90 with alternate half-cycles being shunted through the diode 89. This results in an outputfrom the outputtransistor91 of the opto-couplerwhich is supplied to a diode 79 which, togetherwith the diode 78, forms an OR gate.

The oscillator is thereby caused to provide a signal to drive the buzzers 16 ofthe desk pad units 13 when a ringing signal is received on the external line and the system is in the intercom mode. The outputfrom the outputtransistor 91 is also supplied to a diode 92 which, together with the diode 45, forms an OR gate.

This causes the light-emitting diodes 15 of the desk pad units 13 also to be driven on receipt ofthe ringing signal.

lfthesystem is in use in the normal telephone mode when the system is placed in intercom mode by operation of one of the push buttons 14, signals are simultaneously applied to the two inputs ofthe AND gate 44 from the line detection circuit and from the output of the flip-flop 49 so as to produce an output which energisesthecoil 85 of a hold relay byway of a drive amplifier 84. This in turn closes the relay switch 86 to connect a hold resistance 87 acrossthe external line to place any incoming call on hold.

In operation, when the system is in the normal telephone mode and an incoming call is received, the ringing circuits in the two telephones will be operated in the normal way. Eithertelephone may answerthe call. If the two telephones are engaged in the intercom mode, the incoming call will actuate the buzzers 16 on the desk pad units 13 and will atthesametimeflash the light-emitting diodes 15 at the cadence ofthe ringing.

When the telephones are being used in intercom mode and an incoming call is indicated by the light-emitting diodes 15 and buzzers 16 of the desk pad units 13 being activated, either caller may actuate the push button 140n his desk pad unit 13 in orderto clock the flip-flop 49 and answerthe incoming call. Either caller may then take the incoming call, and the other callermay replace his handset. Furthermore an incoming call may easily be transferred from one callerto the other by operation of the push button on one ofthe desk pad units 1 3to simultaneously put the external line on hold and sound the buzzers 16 in both desk pad units 13. The parties on the two telephones may then talkto each other with full security from the incoming call, and the second party may obtain the incoming call simply by pressing the push button 14 on his desck pad unit 13, the first partythen replacing his handset.

When an intercom call is required, the initiating party presses the push button 14 on his desk pad unit 13, thus placing the system in intercom mode and operating both buzzers 16, and lifts his handset. When the other party answers by lifting his handset, the connection is made and the audible indication ceases.

Claims (13)

1. Atelephone control system ofthe tyoe defined comprising a central control unit including line connection means for connecting each of a plurality of telephones to an outside line and intercom connection means for connecting each of a plurality of telephones to one another, and a respective local control unit which is intended to be placed in proximity to each telephone to beconnected to the system and which includes indicating means for indicating an intercom callfrom another local control unit and actuating means which, when actuated, operates the indicating means of another local control unit.

2. A system according to claim 1, wherein the indicating means is an audible andlor a visual indicator.

3. A system according to claim 1 or2,whereinthe actuating means is one or more push-button switches.

4. A system accordingtoclaim 1,20r3,wherein each local control unit is connected to the central control unit by way of a respective line jack unit which also includesterminalsforconnection oftheassoci atedtelephonetothecentral control unit byway of the line jack unit.

5. A system according to any preceding claim, wherein the central control unit includes holding meansforautomaticallyplacing an incoming call on the outside line on hold when the intercom facility is in use.

6. A system according to claim 5, wherein the holding means is arranged to indicate the occurrence of an incoming call when the intercom facility is in use by means ofthe indicating means on each local control unit.

7. A system according to claim 5 or 6, wherein the holding means is arranged to release the incoming call from hold when the actuating means of one of the local control units is operated.

8. Asystemaccordingtoanypreceding claim, wherein the central control unit includes transfer means for placing an incoming call received on one telephone on hold while the call is transferred to anothertelephone.

9. A system according to claim 8, wherein the transfer means is arranged to place the call on hold in response to actuation ofthe actuating means ofthe local control unit associated with the telephone receiving the call.

10. Atelephonecontrol system incorporating active line detection means for detecting when a telephone line is active comprising two comparators each having a respective input coupled to the incoming line and a respective input arranged to receive a reference voltage.

11. Atelephone control system incorporating ring detection means for detecting a ringing signal on a telephone line comprising an optically coupled isolator having its light-emitting section coupled to the line and its light-detecting section arranged to provide a detection signal when a ringing signal is detected.

12. Atelephone control system ofthetype defined in which intercom call and line hold and release are actuated by a single button.

13. Atelephone control system substantially as hereinbefore described with reference to the accompanying drawings.