Telephone system

Sept. 6, 1938.

D. MASTIN!

2,129,332

TELEPHONE SYSTEM

Filed April 8, 1935

<img file="US2129332A_D0001.tif" />

<img file="US2129332A_D0002.tif" />

<img file="US2129332A_D0003.tif" />

<img file="US2129332A_D0004.tif" />

Patented Sept. 6, 1938

2,129,332

UNITED STATES PATENT OFFICE

2,129,332 TELEPHONE SYSTEM Domenico Mastini, Rome, Italy Application April 8, 1935, Serial No. 15,342 In Italy March 20, 1935

Claims.

My invention relates to telephonic or telegraphic connection between two points in which use is made, for a portion of the distance between said points, of any kind of conventional 5 type of telephone network, for example, networks having local or central battery, or an automatic system, wireless transmitting means such as electromagnetic or light waves being used for the remainder of the distance between two points. 10 My arrangement requires no change at the central telephone plant, the only change which is required being at the individual subscriber’s stations where there is added what I call a “complex,” which is used instead of the ordinary in15 dividual telephone instrument, there being a conversation connection combined with said “complex.”

In the accompanying drawing, by means of which I illustrate my invention,

Fig. 1 is a schematic view exemplifying the general principles of my invention, and

Fig. 2 is a diagram of the circuits which I may employ.

The principle of my invention is first explained 25 with reference to Fig. 1, wherein a remote radio station I, either portable or stationary, is to be connected with a particular subscriber station 3 through a central station 5. The radio station I, through radiated energy, effects the remote 30 control of a complex 7, which is associated with a telephone sub-station. Under the actuation of this remote control, the complex 7 is connected with the central station 5, while the ordinary telephone apparatus 9 at the sub-station is discon35 nected from the network, and gives rise to operations in the network circuit of the central station similar to those which would have been produced had the apparatus 9 called the apparatus 3 directly. The radiant energy, mod40 ulated at the remote radio station I, passes to the complex 7, and the voice-modulated current passes over the previously established wire conversation circuit of the telephone network to the subscriber station 3.

Conversely, an incoming call made from any subscriber’s station will actuate a transmitter in the complex 7 tuned to the receiver circuit of the remote radio station I, which transmitter, through the radiated energy, actuates a receiver 50 in the remote station i and upon response of the latter, completes the conversation circuit I—3.

My inventive concept is explained in greater detail with reference to Fig. 2 of the drawing. This figure diagrammatically shows a combined 55 radio-telephone network connection between a (CI. 250—6) remote radio station I and any subscriber 3 of a telephone network, whether of dial or other type.

The diagram of Fig. 2 serves to explain the construction shown in Fig. 1. In Fig. 2 there 5 is the remote, the stationary or movable radio station I, the interposed complex 7, the telephone apparatus 9 connected with the local station, and the telephone central 5. The station I consists of a transmitter Π and a receiver 19, 10 with the corresponding aerials. The complex 7 consists similarly of a stationary wireless transmitter 2i and a receiver 23, with the corresponding aerials.

Two cases are now possible: 15 (1) The radio station I calls any subscriber’s station 3.

(2) Any subscriber’s station 3 calls the radio station I.

In case 1 the conversation circuit is established 20 in the following manner: As long as a microphone 25 at the radio station I is hung up, the transmitter 17 of station I is inoperative, and both microphone and the transmitter circuits are open. Upon the lifting off of the micro- 25 phone, however, both circuits are closed by the hook 27 and the transmitter begins to send a carrier wave and, so long as there is no modulation, continues sending this carrier wave which is received by the stationary receiver 23, is am- 30 plified in high frequency amplifier 29, and is passed on to a detector tube 31. In this case the detected high frequency oscillations produce a direct current and this will give rise to a potential at the ends of a variable poten- 35 tiometer 33 in the cathode circuit of the detector. A portion of this potential is passed to a low frequency amplifier 35, while the total potential drop acts on the grid circuit of a subsequent tube 37. This tube 37 is directly cou- 40 pled with an amplifying stage (tube 39), the function of which is to amplify both the modulated current and the direct current.

A bridge system is provided in the plate circuit of the tube 39 across the points (apices) 45 of which there is connected an impulse relay 41 which is connected in series with a milliammeter 43. By suitably adjusting a regulating resistance 45 in the bridge, the latter, in the absence of a carrier wave, can be set to zero, or 50 balanced.

On the other hand, if a carrier wave is transmitted, a potential variation will take place, the bridge is no longer in balance, the milliammeter indicates the passage of current, the relay 41 is 55

2,129,332 excited and closes the feed circuit of a relay 47. The relay 47, with the switches 49 and 51, shifts the telephone line, consisting of the wires 53 and 55, to the non-local circuit, these wires 53 and 5 55 being then connected through two transformers 57 and 59 with the output circuit of the stationary receiver 23 and with the input circuit of the stationary transmitter 21. The same relay 47, through a contact 61, also actuates the stalo tion transmitter 21. An armature 63 also closes the circuit to the central station 5 and opens a shunt circuit normally across the transformer 59. Calling impulses coming in from station I may then be sent over the line to the central station. 15 The oscillator grid circuit of the transmitter 17 is connected to the movable element 65 and to the upper contact 67 of a dialing device 69; A lower contact 71 is also associated with the element 65 and the terminals of a grid biasing bat20 tery 73 are connected, respectively, to the contacts.

The grid biasing battery, therefore, is intermittently interposed in the grid circuit of the oscillator by actuation of the dialing device, the 25 polarity of the battery and its potential being such that the grid receives a blocking negative voltage when the said battery is in circuit. When the element 65 is in the position of rest, as shown in the drawing, the oscillator may func30 tion normally.

The interruptions of the oscillating current, or of the carrier wave, corresponding to the desired subscriber’s number, operate, at the receiver 23, to cause the relay 41 to vibrate and 35 thus impose upon the telephone lines 53—55 the number of pulses required for the calling of the desired subscriber 3.

When this is done and the subscriber’s station 3 is not busy, conversation can be begun, as the 40 modulations coming from the movable transmitter are sent into the wire circuit by the stationary receiver 23 and the coupling transformer 57, while the modulations emitted by the wire circuit pass through the coupling transformer 59 to the 45 stationary transmitter 21 and from there, by wireless, to the movable receiver ί 9.

In the second case (2), when the call goes out from any subscriber 3 of the telephone network a slow release relay 75 is actuated thereby. This 5Q relay is of the thermic type and, after being energized, holds the armature attracted for thirty seconds or for any other suitable period of time. A contact 77 of this relay actuates the transmitter T and a contact 79 actuates a buzzer 81, in 55 the grid circuit of transmitter 21. The transmitter 21, therefore, will send oscillations, which are modulated by the inherent frequency of the buzzer and which are received by the movable receiver 19 and passed to the associated tele60 phone apparatus 83. There they produce a call and, if it corresponds to the number of the sta-. tion I and is answered, microphone 25 will be taken off. As a result, the movable transmitter 17 now sends a carrier wave which, after ampli65 flcation and reception through the stationary receiver 23, actuates the relay 4i therein, which establishes the conversation circuit. Relay 41 actuates relay 47 which switches in the telephone line and at the same time closes the feed cir70 cult of the stationary transmitter 21, which was previously closed for a short time through the relay 75. After these operations the wireless conversation circuit is-established.

When the telephone network is manual rather 75 than of the dial type, the plant is simplified, it being sufficient to establish connection with the central exchange in the manner described previously, and, in a central having local batteries, to send out another calling current.

The circuit described herein only by way of 5 example may be modified in different ways. For example, other rays, for example, light rays, may be employed instead of radio connections.