FIELD AND BACKGROUND OF THE INVENTION The present invention relates to telephony, and particularly to a telephone adaptor (or jack) unit for connecting telephone handsets to a telephone line.

A subscriber's telephone line usually includes a number of extensions enabling different handsets to transmit and receive via the same telephone line. Many sophisticated systems are available providing, among a wide variety of various telephone functions, the function of connecting a selected extension to the telephone line, or connecting a plurality of extensions at one time to the telephone line to provide intercommunication between the extensions. However, such known sophisticated systems are generally very complicated and costly, and are therefore generally utilized only by commercial concerns, as distinguished from residential subscribers which may have but a few extensions connected to one telephone line and which do not require many of the functions of a sophisticated system.

OBJECTS AND BRIEF SUMMARY OF THE INVENTION An object of the present invention is to provide a telephone adaptor unit particularly useful

by residential subscribers to permit the telephone line to be used for many of the serves now provided by sophisticated, costly telephone systems used by commerical concerns.

According to the present invention, there is provided a telephone adaptor unit for a telephone handset connectible, with other like telephone adaptor units for other telephone handsets, between the respective telephone handset and a common telephone line, comprising: an off-hook detector for detecting whether the respective telephone handset is off-hook, on-hook, or momentarily on-hook; a first switching device effective, when the respective off-hook detector detects an off-hook condition, to connect the respective telephone handset to the telephone line and to disconnect the other telephone handsets from the telephone line; an audio circuit including an audio amplifier and speaker connected to the telephone line; a second switching device for enabling the audio circuit to receive audio signals from the telephone line and to reproduce such signals via its speaker; and a control system effective, when actuated, to actuate the first switching device of the other telephone adaptor units to connect their respective telephone handsets to the common telephone line, and to actuate the second switching device of the other telephone adaptor units to enable the audio circuit of the other

telephone adaptor units to receive audio signals from the telephone line and to reproduce such signals via their speakers.

According to the preferred embodiments of the invention described below, the control system also includes time delay means effective, upon actuation of the control system, to actuate the first switching devices of the other telephone adaptor units only for a first predetermined time interval, and to actuate the second switching devices of the other telephone adaptor units for a second predetermined time interval.

According to further features in the described preferred embodiments, the control system includes a signal detector connected to the output of the line status detector, a first time delay circuit connected between the signal detector and the first switching device, and a second time delay circuit connected between the signal detector and the second switching device.

As one example, the first predetermined time interval may be of the order of 20 seconds, and the second predetermined Jime interval may be of the order of 10 seconds.

A telephone adaptor unit constructed in accordance with the foregoing features provides a number of important advantages. Thus, it enables private conversations to be had via one telephone

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handset, which private conversations cannot be heard on the other telephone handsets served by the same telephone line. In addition, the telephone adaptor unit serves as a paging system, enabling a person at one telephone handset to use the built-in speaker in the adaptor unit for paging purposes. The telephone adaptor unit further permits the telephone line also to serve as a home intercommunication system wherein all the telephone handsets are simultaneously connected to the telephone line.

Since the adaptor unit thus includes its own built-in speaker which may be used for paging purposes, for example, such a unit might be called a "talking jack".

Further features and advantages of the invention will be apparent from the description below.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein:

Fig. 1 is a block diagram illustrating a telephone line equipped with a plurality of telephone adaptor units constructed in accordance with the present invention;

Fig. 2 is a block diagram illustrating one construction of one of the telephone adaptor units in the system of Fig. 1 ; and

Fig. 3 is a block diagram illustrating a modification in the construction of the telephone adaptor unit of Fig. 2.

DESCRIPTION OF PREFERRED EMBODIMENTS With reference first to Fig. 1 , there is illustrated a telephone line including two wires 2a, 2b, such as may be provided a subscriber in the subscriber's home. The subscriber is further provided with a plurality of telephone handsets 4a, 4b, 4c each connected or connectible to the telephone line to permit any one of the telephone handsets to use the telephone line for both transmitting and receiving messsges.

In the conventional system, particularly as used by residential subscribers, the connections of the telephone handsets 4a-4c to the telephone line 2a, 2b are done by wall-mounted jacks which permit each telephone handset to be selectively connected to the telephone line. According to the present invention, such telephone jacks are used for receiving a telephone adaptor unit, shown at 6a, 6b and 6c in Fig. 1, for connecting the telephone handsets 4a-4c to the telephone line 2a, 2b in such a manner to enable the

telephone line to be used for other functions, including paging and intercommunication, as will be described below.

Fig. 2 illustrates one construction, generally designated 6, of one of the telephone adaptor units 6a-6c. As shown in Fig. 2, the telephone adaptor unit 6 is connected to the telephone line (2a, 2b, Fig. 1) via a wall jack 8 and to the respective telephone handset (4a-4c, Fig. 1) via a telephone connection 10.

Thus, the telephone adaptor unit 6 illustrated in Fig. 2 includes an off-hook detector 12 for detecting whether the respective telephone handset is off-hook, on-hook or momentarily on-hook ("flashing hook") . The off-hook detector 12 also controls a switching device 14 which, when the detector detects an off-hook condition in its respective handset, connects its respective handset to the telephone line and disconnects the other telephone handsets from the telephone line.

For example, in the illustrated example the telephone line carries a +48 volt when all the telephone handsets are in an on-hook condition. As soon as a detector 12 in one adaptor unit 6 senses an of -hook condition in its respective handset, the detector actuates its switching device 14 to connect its handset to the telephone line. This causes the

voltage on the telephone line to drop such that the switching devices 14 in the adaptor units for the other telephone handsets are disabled from connecting their respective handsets to the telephone line. Thus, as soon as one telephone handset goes off-hook to connect its handset to the telephone line, all the other telephone handsets are disconnected from the line, thereby permitting the off- hook handset to use the line privately.

The telephone adaptor unit 6 illustrated in Fig. 2 further includes an audio circuit connected to the telephone line including an audio amplifier 16 and a speaker 18 driven by the amplifier. The audio amplifier 16 is energized by a self-contained power supply 20, such as a rechargeable battery, via a power supply switch 22. Normally, switch 22 is open, thereby disabling the audio circuit.

Each telephone adaptor unit 6 as illustrated in Fig. 2 further includes a line status detector 24. Detector 24 continuously detects the status of the telephone line, i.e., to detemine whether all the telephone handsets connected to the line are "on-hook", or whether one is "off-hook". In the illustrated example, this can be determined by sensing the voltage on the telephone line, it being +48 V in the all "on-hook" condition, and at a lower value when one of the handsets goes "off-hook".

Detector 24 particularly detects a momentarily off-hook condition, or a "flashing hook", e.g., by the user momentarily or repeatedly operating the off-hook lever of the telephone handset. When such a condition is sensed by detector 24, it actuates a signalling detector 26 which in turn actuates two timers 28, 30. Timer 28 is actuated to close the switching device 14 in the respective adaptor unit for a predetermined time interval, and thereby to connect all the telephone handsets to the telephone line for this predetermined time interval. Timer 30 is effective to close the power supply switch 22 connecting the power supply 20 to the audio amplifier 16, and thereby to enable the audio amplifier to drive the speaker 18 from the telephone line for another predetermined time interval.

The telephone adaptor unit illustrated in Fig. 2 operates as follows:

When all the telephone handsets (4a-4c, Fig. 1 ) are on-hook, a +48 V appears across the telephone line (2a, 2b, Fig. 1). Also, switch 22 is open so that the audio circuit including speaker 18 is disabled.

As soon as one telephone handset goes off- hook, this is detected by detector 12 in the telephone adaptor unit 6 for the respective handset. Detector 12 actuates its switching device 14 to connect the

respective telephone handset to the telephone line. When this occurs, the +48 V across the line now drops, so that the switching devices 14 in the other telephone adaptor units are disabled from connecting their respective telephone handsets to the line.

It will thus be seen that the telephone adaptor unit 6 enables the first telephone handset which goes off-hook to seize the line and to engage in private conversations which cannot be heard on the other telephone handsets.

Should a user of one of the telephone handsets wish to page a person via the telephone line and the handsets connected thereto, this may be done by going off-hook at one of the telephone handsets, thereby connecting that handset to the telephone line. But this also disconnects the other telephone handsets from the line as described above. However, the off-hook handset may then momentarily go on-hook or "flashing-hook", whereupon the line status detector 24 of all the other telephone handsets produces an output signal via detector 26 to actuate the two timers 28 and 30. As described above, timer 28 actuates the switching device 14 in its respective adaptor unit to connect its respective telephone handset to the telephone line for a predetermined time interval; and timer 30 closes the power supply switch 22, also for a predetermined time interval, thereby enabling the audio

amplifier 16, receiving audio signals from the telephone line, to drive the speaker 18.

Accordingly, during the time interval of timer 30, the user of one telephone handset may talk into the handset in order to page a person, and the spoken words will be transmitted via the telephone line to all the other handsets connected to that telephone line.

It will thus be seen that when a user momentarily or repeatedly products an on-hook signal (a flashing signal) by the use of the respective telephone handset, all the telephone handsets will be connected to the telephone line and the audio circuit including amplifier 16 and speaker 18 will be actuated so as to permit paging via all the telephone handsets for a predetermined time interval determined by timer 30. As one example, timer 30 may have an interval in the order of 10 seconds, thereby permitting a person to be paged for 10 seconds after the "flashing signal".

It will also be seen that, when the "flashing signal" is produced at one telephone handset, all the telephone handsets are connected to the telephone line for a period of time determined by timer 28, enabling any of the other telephone handsets to go off-hook and thereby to be simultaneously connected to the line so as to provide intercommunication between the headsets. s one example, the period of time by timer 28 is in

the order of 20 seconds. When that period of time runs out, if no other telephone handset has gone off-hook, the other telephone handsets are disconnected from the line; but if one other handset has gone off-hook, then it remains connected to the line when the 20 seconds have elapsed.

Fig. 3 illustrates a variation in the construction of the telephone adaptor unit shown in Fig. 2. The essential difference in the variation of Fig. 3 is that a microprocessor 40 is provided to perform the functions of the signalling detector 26, timer 28 and timer 30. In all other respects, the telephone adaptor unit illustrated in Fig. 3 is constructed, and operates in the same manner, as described above with respect to Fig. 2, and therefore the same reference numerals have been used to identify the corresponding elements as appearing in Fig. 2.

While the invention has been described with respect to two preferred embodiments, it will be appreciated that many other variations may be made. For example, instead of the unit being attached to an existing telephone jack, it could be constructed so as to be used instead of a conventional telephone jack or it could be incorporated in an existing telephone handset. Many other variations, modifications and applications of the invention may be made.