US1901958A - Substation circuit - Google Patents

Description

Patented 21, 1933 UNETED STATES LABORATORIES, INCORPORATED, YORK PATENT GFFlCE JOHN W. GOODERHAII, OF LABGEMONT, NEW YORK, ASSIGNGB '10 BELL TELEPHONE OF NEW YORK, N. Y. A CQEPOBATION OF NEW sunsrnrron orreocrr Application area name a, rear Serial 251e, erases.

This invention relates to circuit arrange ments for signaling systems wherein signals may be transmitted from or received at the same station. More specifically, this invention is embodied in a subscribers telephone station or substation, as it is more commonly called, and more particularly in the combination of a substation and a telephone line.

lhe particular substation herein illustrated and described is a modification of a general type described in U. S. Patent 1,254,471 issued to George A. Campbell, January 22, 1918, and particularly the form shown in Figs. 4 and 4A of the said patent,

As stated in the patent to Campbell referred to above, telephone substations of the type therein disclosed comprise a transmit ter, a receiver, a balancing network consisting in the simplest form or an auxiliary resistance and a transformer having a plurality of windings which, in combination with a telephone line are so designed that (l) the transmitter and receiver shall be conjugate, that is, there shall be negligible side tone in the receiver in consequence of the actuation of the transmitter by sound waves; (2) the line and auxiliary resistance shall be conjugate in order that a negligible amount of the energy absorbed by the substation :trorn the line shall be wasted in said auxiliary resistance; (3) for a given line having a definite impedance, the telephonic energy delivered by the transmitter shall be a maximum; {i the amount of energy delivered by the line to the substation shall be a maximum, in other words, the impedance of the substation as seen from the line shall be numerically equal to the impedance of the line; (5) at a small sacrifice of eiiiciency it shall be possi-= ble to discriminate efi'ectively against disturbing line noise as distinguished from the telephonic signals from the communicating station.

A substation satisfying the above men tioned requirements is ideal in that its overall efiiciency from the transmitter of one station to the receiver of the communicating substation is the theroretical maximum which cannot be exceeded by any two similar invariable substations whether satisfying the requirement of transmitter and receiver conjugacy or not. It is further ideal in that a minimum number of elements is employed since at least one auxiliary ele ment is necessary to secure freedom from side tone.

It is an object of the present invention to adapt a circuit of the general type mentioned above to particular system requirements with economy of parts and simplification of wiring and assembly. r

In the case of a. common battery, anti-side tone substation circuit, it is desirable from a transmission standpoint that the capacity of the condenser, which is necessary to maintain all direct current from the line through the transmitter, be larger than the capacity of the condenser which is connected in series with the ringer. This requirement means that two condensers must be employed in the substation circuit,

In the case of a substation it is usual to provide a box which is commonly called a subset and in which is housed the ringer, the induction coil or transformer and the balancing network. ed b means of a cord having a pluralit of con actors to adeslr stand or handset w ich comprises the switchhook, receiver, and transmitter, and in the case of dial systems also includes the dial.

The invention provides a circuit in which these features are present and in which a minimum number of conductors is used for connecting the subscribers set to the handset or desk stand.

Another object of the invention is the pro vision oi means for decreasing interference effects on neighboring electrical circuits (e. g. radio sets) caused by the pulsations trans lhis subset is connect mitted over the line when a dial is operated V at the substation. a

@ther and further obJects of the invention will be clear from the following description Fig. 2 is a diagram showing the circuit of Fig. 1 in greater detail;

ig. 3 is a practical arrangement of a substation fundamentally like t at of Fig. 2 in l which a so-called desk stand or wall set equipped with a dial is used;

Fig. 4 is a practical arrangement of a sub station fundamentally like that of Fig. 2 in a which a so-called hand set equipped with a dial is used;

Fig. 5 is a modification of the desk stand or wal set circuit connections shown in Fig. 3;

Fig. 6 is a modification of the hand set cirsuit connection shown in Fig. 4.

Referring to Figs. 1 and 1-A, a telephone line L is connected to a substation comprisin a transmitter T, a receiver R, and a threewindin transformer having two low resistance windings 11 and 12 and a high resistance winding 13 (which may include an auxiliary resistance X), said windings being on a common core and preferably having very small leakage.

mitter T, receiver R, high resistance winding 13 and low resistance winding 11 are connected together at a common point 14. The other terminal of the low resistance winding 11 is connected to one side of the line L at 15,

the other terminal of the receiver R and the other terminal of the high resistance winding 13 (when the auxiliary resistance X is part of the winding 13) are connected togather and to one terminal of the low resistance winding 12 at 16. The other terminal of the low resistance winding 12 is connec to the other terminal of the transmitter T and the other side of the line at 17. When it is desired to exclude the battery supply current from the receiver R and winding 12, a condenser 18 may be inserted preferably be" tween the winding 12 and the connection of the transmitter T and the line L at 17.

The theory of operation of the fundamental t of substation shown in Figs. 1 and 1-A is the same as that described for Figs. 4, 4a, 5 and 6 in the above-mentioned Campbell Patent 1,254,471 except that the fact that the low resistance winding 11 has been placed in the opposite side of the line must be taken into consideration. This low resistance winding 11, when located as shown in Fi s. 1 and 1-A simplifies the construction of t e induction coil in that it can be made with but four external connections and also simplifies the switchhook and cording arrangements which can be used with the circuit.

Fi 2 shows the circuit of Fig. 1 to which has n added a switchhook 19, contacts 20 and 21 and a pair of contacts 22. When the receiver R is removed from the switchhook 19, the contacts 20 and 21 are in contact with the switchhook 19 and the pair of contacts 22 are closed as shown. Placing the receiver R on the switchhook 19 opens the nor- One terminal of the trans-.

ted A---A mally closed contacts 22 thereby opening the circuit from the line L through the condenser 18, windin 12, auxiliary resistance X, winding 13 an winding 11, and also opens the circuit of the transmitter T and receiver R. A callin device 23 is bridged across the line L in series with denser preferably has a. capacity between mi. and 1 11115.

An induction coil which has been found satisfactory for this type was wound on a spool and mounted on a closed core of laminated silicon steel. The inner winding 11 comprised approximately 940 turns having a resistance of approximately 24 ohms, the inner terminal being arranged to be connected to the line L at 15 and the outer terminal connected to the inner end oi the middle winding 13 at 14. The middle winding 13 and the auxiliary resistance X comprise approximately-245 turns having a resistance of approximately 50 ohms, the outer terminal being arranged to he connected to the inner terminal of the outer winding 12 at 18. The oumr winding 12 comprises approximately 565 turns having'a resistance of approximately 21 ohms. The middle winding 13;. was wound in an opposite direction to that 01'' the inner winding 11 and the outer winding 12. A condenser having a capacity of approximately 2 mi. has been found satisfactory for the condenser 18.

The substation in Fig. 3 comprises a socalled subscribers s t (shown above the line and a so-called desk stand (shown below the line B-B). The subscribers set, and desk stand are connected together by means of a cord. The subscrihers set houses the signaling device 23 with its associate condenser 24 and the induction coil of the type described above in connection with Fig.

2 and its associated condenser 18. It is connected to the line L and provided with five terminals- 25, 26, 27, 28 and 29 in addition to the line terminals." The desk stand comprises the receiver R, transmitter T, switchhook 19 with its associated contacts and 21 and pair of contacts 22 and a dial DL, preferably of the type described in U. S. Patent 1,353,612 to Reeves, September 21, 1920. The desk stand is provided with four terminals 36, 37, 38 and 39. The terminals 26, 27, 28 and 29 of the subscribers set are connected to the terminals 36, 37 ,38 and 39 of the desk stand respectively by means of a four conductor cord. The terminal of the subscribers set is not used when the subscribers set is connected to a desk stand of the typeshown in Fig. 3 and its use will be described later in connection with Fig. 5. A condenser 30, the capacity of which is relatively small, is connected in shunt to the winding 11 of the induction coil when desired. This condenser reduces the interfera condenser 24. This con of subscribers set once on neighboring radio sets caused by the pulsations transmitted over the line from the substation when the dial BL is operated.

The subststion in Fig. 4 is similar to that of Fig. 3 except that e combined transmitter and receiver TR with its associated cradle contact switching mechanism of a type well known in the art a we employed.

The desk stand in Fig. 5 is in general similer to that of Fig. 8. It is provided with five terminals 55, 56, 5?, 58 end 59 which are connected (not shown) to terminels 25, 26, 2?, 28 end 29 respectively of the subscribers set of Fig. 3 by means of a five conductor cord. The switcblioclz contacting arrangement and the dialing contect arrangement have been modified so that the Winding l1 will be included in the path which short-circuits the tiensinittei" T when the dial BL is operated to transmit dialing impulses over the iine. This sliort-circuiting potii may be traced from the transmitter T, terminal 56, cord conductor to terminal 28, coil 11 at 1%. the other terminal of coil 11 st 15, terminal 25, cord conductor to terminates, diel contect 51, to transmitter 'l. This elicit-circuiting of the winding 11 dosing dialing has been found to reduce the interierence efiects on neighboring radio sets csused by the opera.- tion of the dial. With 8. desis stood of the type shown in Fig. 5, the condenser 39 connected across the winding 11 on the induction coil may be omitted The bond set in ois in general simiiei' to that of 4:. it is provided with five terminals $6, 6?, 68,69 and 7% which connected (not shown} to terminels 25, 26, 27, 28 end 23 i'espectively oi the subscriber set of 4 by means of s five conductor cord. Provision is made in the circuit srrsngemerit for the bend sets of Fig. 6 to include the winding 11 oi the induction coil in the shortcircuiting path for the transmitter during dialing in e manner similsi' to tiiet employed in the desk stead of Fig. 5.

The invention is slso capable of other modificstions end adaptations not specifically re- Iierrcd to but included within the scope of the epuended claims.

Wbet is claimed l. A signeling circuit including in series four components, the first of said components including o iine, the second oi? ssid components including a winding of e trensicrmer, the third of said components including o. receiving instrument in persllel with e series errengement of e lie-lensing impedence means end e second winding of said trensiormer, the fourth of seid components including a third winding of said trensiormer, e. tronsmitting instrument connected in shunt with a series connection "of said first end second components, said three windings being termineted on four terminals and having a common magnetic field, s contact common to said transmitting instrument, said receiving instrument and two of said transformer windings, a shunt circuit for said transmltting instrument, an impulse sending device and contacts controlled by said device for opening the circuit of said receiving instru ment and closing the shunt circuit whenever said device is moved from normal.

2. A signaling circuit including in series four components, the first of said components including a line, the second of said components including a winding of a transformer, the third of said components including a receiving instrument in parallel with a series arrangement of a balancing impedance means and a second winding of said transformer, the fourth of said components including o: third winding of said tronsformer, a transmitting instrument connected in shunt with a series connection of said first and second components, said three transformer windings being terminated on the four terminals, 21 contact common to said transmitting instrument, said receiving instrument said second winding and said third winding, normally open circuits for said transmitting instrument and said receiving instrument and said line, and means for closing said circuits.

3. A telephone system adopted for use with a common buttery system including in series our components, the first of said components including a, line, the second of said components including a winding of a transformer, the third or" said components including a receiving instrument in parallel with a, series arrangement of s balancing impedance means and a second winding of: said transformer, the fourth of said components including a third winding of said transformer, a transmitting instrument connected in shunt with the series connection of said first and second components, said three teensiormer windings being terminated on four terminals, e contact common to said trons mitting instrument, said receiving instrument, said second winding and said third winding, normally open circuits for said re ceiving instrument and said transmitting instrument, means for closing said circuits, an impulse sending device, means actuated by said device for transmitting impulses, end mesns actuated during the operation of said sending device for opening the receiving instrument circuit and shunting the transmit ting instrument circuit and one of the windings of said transformer.

4-. A signaling circuit comprising a. tronsformer, a path for the transmission end reception of signals, a path including o transmitting apparatus, a path including 3. winding of a transformer, a resistance end a. receiver, said receiver being included in a path shunted about said winding of said trons former and said resistance, said last menill!) tioned path and a second winding of said transformer being included in a series circuit, said series circuit being shunted about said transmitting apparatus, said first mentioned path and a third winding of said transformer being included in a series cit cuit shunted about said transmitting apparatus, said three transformer windings hem terminated on four terminals, said thir winding of said transformer, said receiver, said transmitting apparatus and said first mentioned winding of said transformer having a common contact with respect to alternating signaling current.

5. In a two-way signaling system, a circuit for the transmission and reception of signals, a normally open transmitting circuit proper, a normally open receiving circuit proper, a balancing circuit, a transformer with three windings terminated on four terminals, said elements being so proportioned and related that said receiving circuit and said transmitting circuit proper are conjugate, contacts actuated by a switchhook for closing said normally open transmitting and receiving circuits, a receiving instrument in said receiving circuit, said receiving instrument being connected, through switchhook contacts, from a point common to two of said windingsto a point common to a difierent pair of said windings.

6. A circuit according to claim 1 in which said transmitter, receiver, contacts and impulse sendingdevice are grouped together and separated from said transformer, and a fourconductor cord interconnects the elements so grouped and the windings of said trans former.

In witness whereof, I hereunto subscribe my name this 27th da of Februar 1931.

, JOHN iv. eoonnhnm

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