GB2228649A - Telephone apparatus - Google Patents

Abstract

A circuit for preventing more than one of a plurality of separate electronic/electric units (3) connectable with further electronic/electrical equipment by way of a telephone type communication connection (2) from simultaneous operation, comprising a control circuit (1) which on initiation of the operational connection of any one of said units (3) with said communication connection automatically prevents operational connection by way of said communication connection. <IMAGE>

Description

COMMUNICATION APPARATUS This invention relates to telephone systems and apparatus.

In particular, the present invention is concerned with systems and apparatus for the control of the operation of handsets, multiple or otherwise or other apparatus operationally coupled into a common input telephone line.

Traditionally a subscriber is connected to a telephone exchange by way of a hard-wired connection between the subscriber's premises and the nearest local telephone system main feeder or the like.

Historically, in the absence of an 'in-house' exchange, electronic switching systems or the like, a line has been involved for each subscriber handset.

However, there has developed increasing demand by subscribers to have more than one telephone handset unit or other apparatus involving a telephone line available in their premises so as to obtain the convenience of being able to use the telephone and/or other apparatus without it being necessary always to have to go to a single fixed or dedicated location.

It has been found, in practice, that with many telephone multi-handset installations whenever one handset or other piece of equipment is in use any other apparatus i.e., handsets that may be associated with the system remain fully operative in the sense that any other person can listen-in to an already established connection or can otherwise attempt to use the phone i.e., start to dial.

These possibilities particularly the latter, can create real problems in the use of many installations particularly multi-unit handset installations since many people use the telephone by lifting the handset and immediately starting to dial prior to placing the handset to the ear. In other words, a second person frequently does not check whether ot not the telephone is already in use before attempting to dial.

Whilst this may not always adversely interrupt a user line connection that may have already been established for the purposes of a standard telephone conversation, problems have been found to arise when the telephone has been connected to the telephone subscriber line by way of the so-called modem and the user connection that has been made is a data type connection, in that any post connection attempt to dial from a second telephone handset operationally connected to the subscriber line or to start other apparatus connected to the line can produce a voltage pulse or glitch which corrupts the data connection.

The present day common requirement by subscribers to connect two or more handsets to a common subscriber line has resulted in the provision of various relatively complex circuit arrangements, which in general involve relatively expensive installations providing for several handsets other other pieces of equipment to be coupled in parallel to a single input telephone line.

The provision of such arrangements is not always acceptable to a telephone subscriber who often requires the capability of being able to provide a multi-unit handset connection system or to use other apparatus involving telephone communication without involving installation complications.

It is an object of the present invention to provide a improved method and means for controlling the operation of at least two pieces of apparatus, such as telephone handsets, connected in parallel with a single subscriber telephone line.

Broadly, acccording to the invention there is provided apparatus for controlling operation of a system requiring availability of at least two electronic/electrical units utilising telephone communication lines such as telephone handsets to be connected to a single subscriber line there is provided means, adapted for interpositioning i.e., effecting connection between a standard telephone subscriber line connection of a telephone system and the units i.e., handsets, for preventing more than one piece of apparatus i.e., a telephone handset of an installation involving at least two said pieces of apparatus connected in parallel with the subscriber line from being operative at any one time, the arrangement being such that when any one of the units connected in parallel to a subscriber line is operative the remaining units is/are rendered inoperable.

According to a further aspect of the invention there is provided apparatus for preventing more than one of a plurality of separate electronic/electric units connectable with further electronic/electrical units by way of a telephone type communication connection from simultaneous operation, comprising a control circuit which on initiation of the operational connection of any one of said units with said communication connection automatically prevents operational connection, by way of said communication connection, with any other unit or units.

For a better understanding of the invention and to show how to carry the same into effect reference will now be made to the accompanying drawing in which: Figure 1 is a schematic circuit diagram illustrating a first embodiment of apparatus incorporating the features of the invention; and Figure 2 is a schematic circuit diagram illustrating a second embodiment of apparatus incorporating the features of the invention.

Referring to the drawings and particularly to Figure 1, the circuit shown therein essentially comprises a control circuit 1 which, when interposed between a telephone subscriber line 2 and two or more handsets 3A,3B.....

which are required to be connected in parallel with the line 2, ensures that whenever any one of the thus connected handsets 3A;3B; , is brought into use the control circuit is arranged automatically to reduce the operational voltage levels that would prevail at any other of the parallel connected handsets to such an extent that the voltage levels are insufficient for sustaining operation of any other handset.

The circuit 1 incorporates a bridge type rectifier circuit 4 including diodes 5,6,7 and 8, connected in bridge formation between nodes 9,10, 11 and 12 as shown.

The diodes are in the embodiment shown are those with the commercial identification nomenclature 1N4003. The nodes 10 and 12 connect with a load circuit 13. The load circuit 13 comprises a silicon controlled rectifier 14 connected across the nodes 10 and 12. The silicon controlled rectifier in the embodiment shown is known under the a commercial nomenclature BT149B. Series connected resistors 15 and 16 and a diode 17 known under a commercial nomenclature BZX79C22 are connected in parallel with the silicon controlled rectifier 14. A capacitor 18 is connected across the resistance pair.

The load circuit effectively provides a voltage dropping arrangement which reduces i.e., effectively short circuits the voltage levels normally used in the standard telephone system to a level which, if applied to a telephone handset cannot initiate or sustain user operation thereof.

The node 9 is connected to receive input from telephone connector unit 19 which connects with the subscriber line 2.

The node 11 is connected by way of a connection line 120 to sockets 21 into which the plugs (not shown) of the handsets 3 are intended respectively to engage. In the Figure the connections of individual handsets and sockets are identified with appropriate letters A,B. That is lines 20A,20B connect with sockets 21A, 21B into which the plugs (not shown) of the handsets 3A, 3B are intended respectively to engage.

The connection unit 19 provides the additional connections required for the completion of standard telephone connections to handsets 3, these additional connections being made to each handset 3 and are schematically shown at 22 with individual handset connections identified. as 22A and 22B.

The control circuit as above discussed is intended to be housed in a casing (not shown) which is adapted for plug-in connection to the conventional subscriber line socket connection and also to provide output- connection to any handset sockets for two or more handset connection plugs.

The connector unit 19 is effectively able to connect, as is conventional, all of the handsets 3 through to the subscriber line whereby each handset 3 is capable of responding to an incoming call or initiating an outgoing call.

When a user lifts any one of the handsets 3 either as an initiating action or in response to indication of an incoming call the control circuit 1 is automatically switched into operation.

That is to say, as soon as one of the handsets 3 is 'lifted' a circuit for the handset being used is automatically completed by way of the connector 19 to the subscriber line 2.

Upon the lifting of the handset the bridge rectifier arrangements 4 become unbalanced and in so doing leads to the production of a voltge drop over the diode 17, and the resistors 15, and 16 thereby to produce the requisite trigger voltage for the silicon controlled rectifier 14 to cause the latter to 'fire' thereby to produce such voltage drop in bridge rectifier circuit, that those handsets 3 other than the handset that has been brought into use are effectively rendered inoperable since the effect of the load is such that it is not possible for the voltage that would .be normally produced upon the 'lifting' of the hand set to reach the requisite level by reason of the effect of the voltage drain caused by the load circuit being effectively connected into the hand set energisation circuitry.In other words the remaining hand sets 3 are effectively short circuited out of possible operation.

Thus the effect of the provision of the load circuit across the nodes 10 and 12 ensures that, when it is switched into circuit by the unbalancing of the bridge rectifier the output from the rectifier and associated voltage dropping circuit ensures that in so far as any other handset connected in parallel with the handset is concerned the voltages available in the circuits associated with these further handsets, are insufficient to allow use of such handsets.

Referring now to Figure 2 this Figure schematically illustrates a second embodiment of the control circuit in which the number of components involved has been reduced in total as compared with those involved in Figure 1.

In Figure 2 the components include two silicon controlled rectifiers arranged back to back to form a Triac arrangement 23 one suitable Triac type being known under the trade nomenclature MAC97-4. The arrrangement 23 is associated with a 'load' circuit 24 incorporating zener diodes 25, 26 known under the trade nomenclature B2X79C15 which diodes are connected back to back. The circuit 24 also includes a capacitor 27. The operation of the circuit of Figure 2 is essentially such that on operating any one hand set the voltage levels at the zener diodes cause the latter to attain the so-called clamped condition thereby producing pulses which are used to trigger the Trac arrangement 23. Once the Triac 'fires' the circuit 24 effectively short circuits the handsets 3 of the system other than the handset that was operated to cause initiation of the circuit 24.

With this arrangement it will be clear that in the event that a person attempts to utilise any one of the other handsets included in the parallel arrangement there will be insufficient operating voltage available to actuate any such subsequently operated handset so that the latter is to all intents and purposes switched-out of the system.

The control circuits of Figures 1 and 2 are also such that as soon as a telephone call is terminated and the handset is 'replaced' the control circuit automatically returns to its initial quiescent condition in which all handsets are available for use.

It will be appreciated from the above discussions that the invention can provide a device which is readily interposable between handsets and a subscriber line socket and which prevents, when any handset unit or other piece of apparatus connected thereto is in use, any other piece of apparatus i.e., facsimile apparatus, modem, handset also connected thereto from being operated without the need for any wired-in connections or the need for involvement of specialist installation experts.

Whilst the above discussion has been concerned with plug-in devices it will be appreciated that the circuit of the invention could be operationally incorporated into the piece of apparatus i.e., inside the handset or other apparatus itself.

A further possibility is the incorporation of the circuit of the present invention directly into single or multi-connection socket conventionally provided for the termination of a subscriber line into a premises.

It will also be understood that the apparatus of the invention could be provided with extension connections associated with telephone systems.

Claims (9)

1. Apparatus for controlling operation of a system requiring availability of at least two electronic/electrical units utilising telephone communication lines such as telephone handsets to be connected to a single subscriber line there is provided means, adapted for interpositioning i.e., effecting connection between a standard telephone subscriber line connection of a telephone system and the units i.e., handsets, for preventing more than one piece of apparatus i.e., a telephone handset of an installation involving at least two said pieces of apparatus connected in parallel with the subscriber line from being operative at any one time, the arrangement being such that when any one of the units connected in parallel to a subscriber line is operative the remaining units is/are rendered inoperable.

2. Apparatus for preventing more than one of a plurality of separate electronic/electric units connectable with further electronic/electrical units by way of a telephone type communication connection from simultaneous operation, comprising a control circuit which on initiation of the operational connection of any one of said units with said communication connection automatically prevents operational connection, by way of said communication connection, with any other unit or units.

3. Apparatus as claimed in claim 1 or 2, and wherein the control circuit is arranged to control the level of electrical energisation within the units, whereby once any one of said units has been caused to operate the control circuit prevents operation of any other of said separate units.

4. Apparatus as claimed in- claim 2, and wherein the control circuit is arranged to prevent the electrical energisation in the remaining unit(s) attaining a level sufficient to allow connection to the said communication connection.

5. Apparatus as claimed in claim 2 or 3, and wherein the control circuit is such that following operation of any one of said units the voltage levels in the system are so reduced with respect to the remaining ones of the separate units that the latter cannot be operated.

6. Apparatus as claimed in any one of the preceding claims, wherein the control circuit incorporates a load circuit adapted for connection to all of said units, and a bridge circuit which is arranged to be so unbalanced upon operation of any one of said units as to cause the load circuit to prevent the operation of any other unit.

7. Apparatus as claimed in any one of the preceding claims 1 to 5, wherein the control circuit incorporates a circuit adapted for connection to all of said units, and arranged for operational control by a Triac arrangement which is such that upon operation of any one of said units the Triac is caused to operate to enable the load circiut to prevent the remaining ones of said units from being operated.

8. Apparatus as claimed in claim 7, wherein;the load circuit incorporates a zener diode configuration adapted for producing the triggering pulses for the Triac arrangement.

9. Apparatus for controlling operation of a system requiring availability of at least two electronic/electrical units utilising telephone communication lines such as telephone handsets to be connected to a single subscriber line, constructed and arranged to operate substantially as hereinbefore described with reference to the Figure 1 or 2 of the accompanying drawings.