FR2664773A1 - Device for keeping an established telephone connection while re-hooking the handset of the instrument in use - Google Patents

Abstract

The invention relates to an electronic device capable of momentarily keeping an established telephone connection, without any instrument connected to the same line is kept off the hook. The device comprises a voice frequency decoder which activates a time-delayed relay for telephone line acquisition when it recognises the code sent by the star key or the crosshatch key of an ordinary telephone instrument. One single device allows several telephone instruments to take advantage of the momentary preservation of the established line.

Description

DEVICE FOR STORING A COMMUNICATION
ESTABLISHED TELEPHONE WITH HANGING
THE HANDSET OF THE POSITION IN SERVICE
The invention relates to an electronic device capable of temporarily maintaining an established telephone call, without any station connected on the same line being kept off hook.

When a person has several telephone sets connected in parallel on the same line and wants to change the station without losing the connection with his correspondent, it is usual for him to leave the first handset off the hook to go and pick up another combined; then, after picking up the second, that it asks a third person to hang up the initial handset. She must listen to the call to know when she can put the handset back on the cradle. If the person on the line is alone, he must leave the first handset off-hook at the risk of forgetting to replace it once the call is completed.

In industrial or commercial premises, the disadvantages of this procedure are even more obvious when it comes to asking someone else to take a communication intended for him. If he is far from the telephone set or if he is busy with a task which he cannot stop immediately, the initial person must wait on the spot until the called party can go to the neighboring station, then he must ensure that the conversation is well underway before hanging up the first handset, a noisy and boring action for people on the line.

In workshops or collective offices, it is usual that the whole community is disturbed in its work by these maneuvers which are in fact a simple exchange of telephone communication between two people.

The device which is the subject of the invention makes it possible to remedy these drawbacks, by giving the first person called the possibility of immediately hanging up his handset without however cutting off the already established telephone communication.

Figure 1 shows schematically the connection of several telephone sets in parallel on the same telephone line represented by its two active incoming wires (1 and 2).

Each station can be connected to the two line wires (1 and 2) using the usual contactors marked 3, 4 and 5 for example.

The device (6) object of the invention, is connected either to an additional contactor (7) or to one of the contactors used because its own connector is of the pull-out type very common today.

FIG. 2 shows the invention which comprises an operational amplifier (8) followed by a voice frequency decoder (9), connected to the selector (10) controlling the triggering of a timer device (11) activating, for a determined time , the relay (12) whose working contact (13) makes it possible to connect the line-take-up resistor (14) between the two wires 1 and 2 of the telephone pair considered.

Before explaining the operation of the device itself, remember that at present modern telephone handsets use voice frequencies to materialize on the telephone pair the digits to be transmitted to reach the correspondent whom one wishes to call. Each of the twelve or sixteen keys of a telephone handset corresponds to a specific audible code, made up of two voice frequencies chosen according to an international standard. These particular codes are issued on the line as soon as a key is pressed.

The operation of the device which is the subject of the invention is as follows: as soon as a telephone call is established and the person present wants to hang up his handset without cutting the connection in progress, it suffices for him to press the key marked with a star (t) to ask the device to temporarily take the line in its place.

As soon as the star code is sent on the line, the system decoder (9) receives it via the amplifier (8). After recognizing and identifying this particular code, the selector (10) specially programmed for this code triggers the timer (ll) which powers the relay (12) for a predetermined time which can be set between 30 and 60 seconds for example. When the relay closes its contact (13), the resistor (14) is connected between the two wires (1) and (2), providing a line socket equivalent to that of a usual telephone set when it is off the hook.

The person present can therefore put down his telephone handset, the device according to the invention totally simulating the presence of a telephone off the hook.

The transfer procedures can then be carried out during the entire time of the time delay, without any telephone set actually being picked up. When the timer has elapsed, the contact (13) opens and the device automatically disconnects, almost inaudibly, if a correspondent is still on the line, or automatically releases the line which is then ready to receive another call. in the usual way.

In a preferred embodiment, the amplifier (8) is provided with a differential input which makes it possible to connect the device to the two telephone wires (1) and (2) via two capacitors t15 and 16) of low value, not exceeding 1000 picofarads but at high insulation voltage. The decoder used is a standard component usually used in telephone exchanges to route the subscriber calls they receive to the desired destinations. At the output, it provides a four-bit binary code which recognizes the key pressed to cause the momentary line seizure via the relay (12). So that this action does not occur during any dialing done to call a correspondent, the device uses either the "star" key (t) or the "dièze" key (or possibly a combination of these two keys With telephone sets having a full sixteen-key keyboard, this device can use the keys marked A, B, C or D.

The device presented finds its application as well in the family environment as in the premises of industrial or commercial activities, either on telephone lines connected directly to the public network, or on internal lines coming from a telephone switchboard.

Claims (5)

 l / Electronic device for temporarily keeping a telephone call established between two correspondents while hanging up the handset in service, characterized in that it comprises in combination a decoder (9) of the voice frequency signals used in telephony, associated with a selector code (10) capable of activating for a predetermined time a line pickup relay (12) as soon as the code selected to cause the line pickup is transmitted for a short time on the telephone line. 2 / Device according to claim 1 characterized in that it is put into service by the simple pressing of one of the keys of the keyboard of a standard telephone with dialing by voice frequencies. 3 / Device according to claims 1 and 2 characterized by the use of the "star" key or the "hash" key, two keys which do not intervene in the numbering used to call another subscriber of the public telephone network. 4 / Device according to claims 1, 2 and 3 characterized in that the establishment of a single device on a telephone line allows several standard phones having undergone no modification to cause the momentary line seizure necessary for the operator can put down his handset without interrupting the call in progress. 5 / Device according to claims 1 and 3 characterized in that it locally uses, at the subscriber of the public telephone network, a voice frequency decoder usually used in electronic telephone exchanges to route calls from subscribers to their correspondents.