US2038427A - Telephonic signaling device - Google Patents

Description

April-21, 1936. A. FRIEDLANDER 2,038,427

' I TELEPHONIC SIGNALING DEVICE I Filed Aug. 20, 1954 2 Sheets-Sheet l April A. FRIEDLANDER ,0

TELEPHONIC SIGNAL LNG DEVICE Filed Aug. 20, 19 54 2 Sheets-Sheet 2 Patented Apr. 21 1936 TELEPHONIC SIGNALING DEVICE Albert Friedlander, Gerardmer, France Application August 20 1934, Serial No. 740,658

In France August 26, 1933 1 Claim.

The present invention has for its object an improvement in telephonic systems, permitting to warn a subscriber talking on the telephone with another subscriber that a third person is calling his number. With the existing system, when a subscriber is talking on the telephone with another subscriber he cannot know that a third person is calling him and trying to enter into communication with him. This often involves serious disadvantages. It is therefore of great interest to provide a device adapted to call the subscribers attention to the fact that someone is calling his number on the telephone.

According to the present invention, I provide, at the telephonic installation of each subscriber, an acoustic or optical, signaling device, such for instance as a special bell, a lamp, etc., adapted to be brought into action, when, in the course of a telephonic conversation with another subscriber, a third person is trying to get into communication with the first mentioned subscriber.

According to a preferred embodiment, this signal can be transmitted through the ordinary telephonic line of the subscriber who is talking by means of a current of a suitable frequency, for instance a musical frequency capable of acting on the diaphragm of the telephonic receiver of said subscriber.

These, and other features, of the present in- .30 vention will result from the following description.

Preferred embodiments of the present invention will be hereinafter described with reference to the accompanying drawings, given merely by way of example, and in which:

Fig. l is a diagrammatical view of a telephonic exchange of the ordinary manually operated type;

Fig. 2 is a diagrammatical view of the special call plug or key to be inserted according to the present invention;

Fig. 3 diagrammatically shows a portion of a multiple exchange of the ordinary manual type;

Fig. 4 shows another portion of this exchange;

Fig. 5 shows the modification according to the present invention;

Fig. 6 shows a portion of an ordinary automatic exchange; and

Fig. 7 shows how this exchange is modified according to the present invention.

Adverting first to Figs. 1 and 2, I will explain 50 the application of the invention to a manual exchange of the simple type. In Fig. 1, I have shown at l the two-wire plug that serves to establish the connection between the exchange and subscriber A. I have shown at 4 the twowire plug that serves to establish the connection between the exchange and subscriber B. 5 is the station of the operator and 6 is the call source.

I have shown at 2 the listening plug of the opera.- tor and at 3 the usual double call plug. The arrows indicate the directions of opening of the 5. various plugs or keys. The operation of such an exchange is well known for someone skilled in the art. In order to make it possible to warn a subscriber already in communication with another subscriber that a third person is trying 10 to enter into communication with him I insert, according to the present invention, in the exchange of Fig. 1, a source of alternating current of suitable frequency (for instance in the simple case that consists in producing in the receiver of $15 the subscriber to be warned a low buzzing, a musical frequency) and a supplementary special key permitting to send this current into the telephonic line of this subscriber. This organ is shown by Fig. 2. This device is to be inserted be- 243 tween points a a and b b of Fig. 1. I have shown at l the source of alternating current of musical frequency and at 8 a special double call plug. Supposing that subscribers A and B are talking together, and that a third subscriber C .5 is trying to enter into communication with one of these two first mentioned subscribers, it sufiices for the operator to move plug 8 either in the direction of double arrow 9 (in order to warn B) or in the direction of double arrow Ill (in order to 30 warn A) and then, eventually to signal occupied to subscriber C, especially advising him that subscriber A or B (according to which of them is being called by C) has been warned.

In Figs. 3 to 5, I have shown the application 3-5 of the invention to a multiple manually operated exchange. In such an exchange there exist several switchboards among which the subscribers are distributed. In each switchboard, there exist, on the one hand, holes corresponding 40 to the group of the subscribers that are calling and on the other hand holes corresponding to the group of subscribers that are to be called. In Fig.

3, I have shown at l l a subscriber line and at f3 a third wire (local wire) permitting the operator to ascertain, in the known manner whether the subscriber that is called is free. At I4, I have shown the jack of a board corresponding to one of the subscribers of the group that can call through this board and at H and i8 jacks of either boards the number of which is determined by the number of subscribers.

In Fig. 4, I have shown at 24, 25, 26 a plug with three conductors, the three ends of which correspond respectively to conductors l5 and I6 55,

of line H, l2 and to ring [4 connected to Wire I3, when the plug is engaged in jack [4, l5, l6. In a likewise manner, plug 36, 31, 38 corresponds to the jack of the subscriber that is called. Between the two plugs of the exchange there exists a known circuit some elements of which, which are necessary for the good understanding of the operation of the device, have been shown in the drawings. Wires 42 and 43 are shown with a certain gap in which are inserted apparatus which are known and have no bearing whatever on the present invention. Conductor 26 of plug 24, 25, 26 is connected to the earth 3!] through'a relay 28 acting on circuit breakers 21 and 3! of line 42, 43 and through a battery 29. I have shown at 23 a relay through which wire I3 is connected to the earth. When plug 24, 25, 26 is inserted into a local jack (such as M, I5, [6) relay 28 is energized, same as relay 23, which is connected in series with relay 28. Wire I3 is given a certain potential with respect to the earth, owing to the resistance of relay 23. This difference of potential is zero if the relay is not energized. Before establishing the connection between A and B, the operator touches, through the end 38 of plug 36, 31, 38, the ring of the jack of the subscriber B that is called. If relay 33, connected to the earth 35 through a battery 34 and acting on contacts 32 and H of line 42, 43, is not energized, wire 38 is connected, through circuit breaker [8, with transformer 48 at the installation of the operator, which includes a receiver '39. If the subscribers line is free, the test relay (corresponding to relay 23 of subscriber A) is open and no difference of potential exists in the local wire connected to the ring. The operator therefore establishes the connection. On the contrary in the line of subscriber B is not free, its test relay is energized and there exists a difference of potential which produces in receiver 39 a characteristic noise signaling that the telephonic line in question is not free.

In Fig. 5 I have shown the auxiliary device according to the present invention, which is intended to warn a subscriber talking with another subscriber that someone is trying to get into communication with him. According to the invention, the arrangement concerning plug B is modified as shown by Fig. 5. In this case also 36, 31, 38 are the three conductors of the plug, 33 is the relay, 34 the battery, 35 the earth, 32 the circuit breaker of line 42, I8 the circuit breaker of line 43 and the listening receiver is shown at 39. I have shown at 52 a source of alternating current of musical frequency and at 45, 46 a double key permitting to warn either of the two subscribers A and B that someone is trying to get into telephonic connection with him. This device is completed by a key 5|, called occupation key, preventing relay 33 from being energized.

In Figs. 6 and 7, I have shown the application of the invention to an improved multiple exchange. In exchanges of this kind, the test no longer exists and the diagram of the plugs is modified in such manner as to automatically prevent a double connection. In Fig. 6, I have shown a portion of the line of Fig. 3 and the modification of the diagram of Fig. 4 concerning plug B in the case of an automatic exchange. I3 is the local wire and I4, l1, and 20 the jack. Relay 23 is replaced by relay 23a completed by a battery 53 inserted between the relay and the earth. In a likewise manner, relay 28 is replaced by a relay B comprising windings 55 and 51 in series, winding 51 having a high resistance. When only plug B is engaged, battery 53 feeds current in series through relays 23a and the resistances 56 and 51. Relay B is caused to work and closes switch 58, which short circuits resistance 51 the current flowing through 56 to the earth at 54. Winding 56 keeps switch 58 closed. If another plug B1 is engaged in a hole, the current will not be any longer sufficient for operating relay B1 mounted in shunt on the low resistance 56.

In order to obtain the working of the supplementary signaling device according to the present invention the structure of plug B is modified as shown in Fig. '7. Relay B is not modified but resistance 51, instead of being directly connected to the earth, is connected to one of the terminals of a more sensitive relay 60 the other terminal of which is connected to the earth at 59. Relay 68 is capable of working under the action of a small current and it is slightly retarded in such manner as to permit the special current to flow only when B shall not have acted owing to the telephonic line being not free. When relay 60 is brought into play, it closes contacts 62 in such manner as to send the special current supplied by source Bl to the subscriber that is called while he is talking with another subscriber. This current is also sent to the person that is calling said subscriber. I

In a general manner, while, I have disclosed, in the embodiments above described, what I deem to be practical and efficient devices, it should be well understood that I do not wish to be limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the present invention as comprehended within the scope of the appended claim.

What I claim is:

In combination, a telephonic system including a plurality of subscribers stations, telephonic lines leading to these stations, an exchange for connecting these lines together, a signal at a subscribers station for warning him, when he is talking with another subscriber, that he is being called by a third subscriber, a signal at said third subscribers station, said exchange including a listening plug, the usual double call plug, a local source of current, a circuit including said source and a special double call plug for connecting said circuit with both of said signals through the telephonic lines of the corresponding subscribers stations.

- ALBERT FRIEDLANDER.

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