US2423127A - Subscriber's station for telephone systems - Google Patents

Description

Patented July 1, 1947 UNITED STATES PATENT OFFICE 7 2,423,127 sonsonrnnias STATION FoRTELEP'HoNE 'SYSTEMS Clement. M. Theillaumas, Lyon, France, assig-nor to International Standard Electric Corporation, New York, N. Y.,-a corporation of Delaware '10 Claims.

The present invention relates to telephone system and more particularly to the circuitslor a subscribers telephone station in rural or other telephone systems with manual or semi automatic service.

One object of the invention is to provide a manually operated or semi-automatic systemineluding, a subscribers telephone station which contains neither a calling magneto nor a local supply battery for the transmitter microphone.

Another object of the invention-is to provide telephone systems of the type described including subscribers station circuits insuring proper operation of these stations with current supplied from anexc-hange.

A still further objector the invention is to provide. ina telephone system including a subscribersstation without magneto or battery, effective means for calling an exchange or another subscriber.

Still a further object of the invention is to pro vide" means whereby the mechanism at asubscribersstation for calling an exchange or an other subscriber without magneto or battery is prevented from interfering with the proper op eration of'the ringer at the subscribers station upon reception of an incoming cal-1.

Still-another object of the invention is to provide-a subscribers station for manual or semiautomaticservicewhich, with regard to a consid erable part of its structurmis similarto and even interchangeable with a subscribers station for full-automatic service.

These and other objects are accomplished, according to the present invention, by the arrange ment and combination of circuits and circuit elements-set forth in the following description, defined in the appended claims and illustratively exemplified intheaccompanying drawing, the single-figure-of which is a wiring diagramof a subscribers telephone station according to the invention and of some of the elements at the exchange to which the subscribers station iscon nected.

Generally, in-the drawing illustrative of this in vention, all contacts-are shown in their rest .positions. V

Thefeed battery l of -the exchange? is permanently connected to the Wires a and h of the line Lover two resistances of suitable value, such as-,;for instance,- of. 5000 ohms each. The line relay 4 is connected across the lime wires wand b in-lseries-with a, for. instance electrolyticycondenser ,5 which serves .tc-isolate the relay at from the battery I; The condenser 4 is, thus; kept 2. charged as long i as the junction between-the e change -B- and the subscribers-station A-remains inactive.

The subscribersstation A contains the receiver 8 and the transmitter microphone l inductively connected in the usualmanner by means of the transformer 8 The ringer -9 is inserted in a circuit loop which isclosed by the lower one of the-contacts I0- of' the cradle switch when-the receiver rests on the-cradle. This loop is inserted between the wiresa andb-through a restcontest of acallingswitch Hand it contains the usual condense-r l 2- to protect the ring-er 9 against direct current; During;- a conversation, the ro ceiver- 6' and the transmitter microphone l" are both connected-to-thissame restcontact'of the switch ll because of the closing of the contacts I3 of the cradle switchwhich are kept open as long as the receiver rests on its cradle orsupport;

The calling device comprises a series of -condensers id'to I dassociated; respectively with pairs of double cont-act switches I l-l8; lt -fll, Zl-ZZ, which,- in their rest positions'shown, connect thecondensers-l l; l5 and-l6 in parallel to the battery lthrough a suitable resistance 23;

thus keepingsaid condensers charged.

The initiation of acall lay the subscriber=necessitatesexcitation of the-line relay dat the exchange B'. This result is accomplished by the discharge "in series of th'e'condensers l4; l5 and I6 which is caused by a simultaneous switching over of all the double contact switches lT-ZZ upon their (right hand) 'working contacts. This operation may be" effected by the subscriber through the operation of a special callingswitch control mechanism; such as'the depression ofa single controlbutton for all said switches or the manipulation of a dial having a single finger hole. The switch I I is mechanically connected with the switches I! to 2|, so asto eliminate during the discharge of the-condensers M- -ifi into the line L the resistance 23 which'would render the discharge current too feeble.

The calling svvitch' control mechanism may be constructed in any desired siiiiple manner. Since it does not form a part of the present invention, it is not shown nor described in detail.

The reception of incoming calls at the subscribers station; presupposes the transmission from the exchange over thewires of the line L of an alternating current 'of lo'w neq-uencyisueh as 16,25 or 50Pi'PLS.) with"apotentia'1 difference wnicnmsyexceeu IOUVbltS'. The'lihgei 9'is thn actuated. alternatin would be aptto cause deterioration oi the electrolytic con densers I l-I6 formed under a much lower tension of about 30 volts, if it were not for the resistance 23. Moreover, this resistance 23 gives to the leakage circuit formed by said condensers a suificiently strong impedance to prevent any interference with the normal operation of the ringer 9.

When the subscriber takes off the receiver, either after emission or upon reception of a call signal, the contact l3 of the cradle switch is closed, so that the transmitter microphone 1 is inserted into the supervisory loop of the operator at the exchange B, and the microphone l is, in this manner, supplied with current over the line L from the exchange battery I. Simultaneously, the contacts are opened, thus disconnecting the leakage circuit through the condensers I4l 6 and the alarm circuit and preventing any weakening of the talking currents.

The line relay I may be protected, instead of by means of a condenser 5, by means of a unidirectional rectifier connected in such a manner that it passes the discharge current of the condensers I4 to 16 while blocking the condenser charging current.

Owing to the omission at the substation of the feed battery for the transmitter microphone and of the calling magneto, it is further possible, according to the invention, to construct a subscribers station which can be adapted to telephone systems with full automatic service as well as to systems with manual or semi-automatic service. The receiver, the transmitter microphone, the induction coil and the ringer can be identical in both cases. Only the electrolytic condensers and the spring contact combinations necessitate a different wiring. Thus, the subscribers stations according to the invention, provide for a more complete standardization of the material and equipment and, moreover, each station in a fullautomatic system can be easily converted into one of a manual or semi-automatic system according to the invention, or vice versa.

The line condensers or the rectifiers to be subsituted therefor, may be provided in the detachable line relay block of a standardized semi-automatic exchange installation. For this purpose, the condensers or rectifiers are inserted into a flat casing mounted on the collapsible rear Wall of the relay support; This requires only a small modification in the wiring on the inside and no change at all in the outside wiring.

It should be noted that the introduction of a subscribers station of the type set forth above into a telephone network with manual or semiautomatic service makes it necessary to hold the wire lines permanently under a current supplied by the exchange battery. However, this permanent application of current has no detrimental efiect upon the insulation of the line, because the potential difierence of the supply battery I does not exceed 30 volts at the end of the charge, whereas, if a call signal is generated by the usual magneto the peak tensions may exceed 200 volts. On the other hand, a high resistance 2, 3 is provided, in the present arrangement, between each terminal of the battery I and the corresponding line wire. Thus, even in the case of a short circuit of the line directly outside of the exchange, the permanent maximum load is less than 3 milliamperes, which is practically negligible. Finally, since the supervision is usually effected by means of a loop at the subscribers station, no danger is involved in introducing into said loop the transmitter microphone 1 to replace a dead resistance.

It will be understood that the invention is not limited to the embodiment shown and described but may be modified or varied in numerous ways within the scope of the following claims.

I claim:

1. A telephone system comprising an exchange, a subscribers station, line wires connecting the exchange with the subscribers station, a supply battery connected across the line wires at the exchange, circuits at the subscriber station including an operator's supervision loop, and a transmitter microphone inserted in said supervision loop, so as to be supplied with current from said supply battery when said supervision loop is closed.

2. A telephone system, as claimed in claim 1, including two high resistances inserted between the terminals of said battery and the corresponding line wires respectively.

3. A telephone system comprising an exchange, a subscribers station, line wires connecting the exchange with the subscribers station, supply battery connected across the line wires at the exchange, a line relay to control outgoing call signals connected across the line wires at the exchange, a blocking device connected across said line Wires in series with said relay to prevent the latter from being excited by the battery current, and an energy storage circuit connected across said line wires at the subscribers station when the latter is not busy, said storage circuit containing at least one condenser, and subscriber controlled means to reverse the connection of said condenser in said storage circuit when a. call signal is to be transmitted from said subscribers station, said blocking means being adapted to pass current impulses emitted from said condenser upon reversal of its connection in said storage circuit to permit excitation of said relay.

4. A telephone system, as claimed in claim 3, in which said storage circuit contains a plurality of condensers normally connected in parallel with one another, and means to connect said condenser in series upon reversal of their connection in said storage circuit.

5. A telephone system, as claimed in claim 3, in which said condenser is an electrolytic condenser.

6. A telephone system, as claimed in claim 3, in which said subscriber station includes a ringing circuit connected across said line wires in parallel with said storage circuit when subscribers station is not busy, said ringing circuit containing a condenser and said storage circuit having a resistance greater than that of said ringing circuit.

7. A telephone system, as claimed in claim 3, in which said storage circuit contains a resistance and means to short-circuit said resistance upon reversal of the connection of said condenser in said circuit.

8. A telephone system, as claimed in claim 3, in which said subscribers station includes a cradle switch capable of assuming a non-busy and a busy position, said cradle switch including a contact connecting said storage circuit to said line wires when said switch is in its non-busy position and breaking said storage circuit when said cradle switch is in its busy position.

9. A telephone system comprising an exchange, a subscribers station, a line circuit connecting said exchange with said subscribers station, a supply battery connected across the line circuit at the exchange, a line relay to control outgoing call signals connected across the line circuit at the exchange, a blocking device connected across the line circuit in series with said relay to prevent the latter from being excited by the battery current, said subscriber's station containing an operators supervision loop including a transmitter microphone, a receiver circuit, a ringing circuit including a condenser, and a storage circuit containing at least one condenser and a resistance, subscriber controlled means at said subscribers station to reverse the connection of said condenser in said circuit and to short circuit said resistance when a call signal is to be transmitted from said subscriber's station, said blocking means being adapted to pass current impulses emitted from said condenser upon reversal of its connection in said storage circuit to permit excitation of said relay, and a cradle switch at said subscribers station capable of assuming a nonbusy and a busy position, said cradle switch in- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Gillette et a1 Mar. 26, 1895 Number

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