US1010478A - Subscriber's telephone apparatus. - Google Patents

Subscriber's telephone apparatus. Download PDF

Info

Publication number
US1010478A
US1010478A US14904503A US1903149045A US1010478A US 1010478 A US1010478 A US 1010478A US 14904503 A US14904503 A US 14904503A US 1903149045 A US1903149045 A US 1903149045A US 1010478 A US1010478 A US 1010478A
Authority
US
United States
Prior art keywords
condenser
receiver
circuit
coil
telephone
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US14904503A
Inventor
Henry P Clausen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Stromberg Carlson Telephone Manufacturing Co
Original Assignee
Stromberg Carlson Telephone
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Stromberg Carlson Telephone filed Critical Stromberg Carlson Telephone
Priority to US14904503A priority Critical patent/US1010478A/en
Application granted granted Critical
Publication of US1010478A publication Critical patent/US1010478A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04QSELECTING
    • H04Q3/00Selecting arrangements

Definitions

  • My invention relates to subscribers tele-- and also of such character that side tones or disturbances the receiver will be cut down or eliminated as much as possible.
  • the side-toneless feature of my invention is, however, claimed in my application, Serial Number 147,322, filed March 11, 1903,
  • my invention may comprise a pair of line conductors 1 and 2, adapted to serve as a party-line for a num-
  • the apparatus at one of the subscribers stations may be of the character shown in. the diagram.
  • the transmitter 3 has one terminal connected with the line wire 1, and its other terminal connected with the hook-switch 4:.
  • the said transmitter and hook-switch may be of any suitable known .or approved construction, the latter, however,
  • the 'receiver' has one terminal connected with the contact 5, and
  • the winding 8 of the induction coil has its other terminal connected with one terminal of the winding 8 of the induction coil.
  • the other contact 6 can be connected with one terminal of the other winding 9 of said induction-coil.
  • the other terminals of the windings 8 and 9 are respectively connected with the three-way condenser 10 and I the line-wire 2.
  • the winding 9 is also connected with another part of the said con-- denser through the medium ofthe conductor 11.
  • the third portion of the said condenser is provided with a conductor leading to ground at 12. In this ground connection,
  • a polarized hell or ringer 13 is located, and around this bell there is preferably a shunt connect-ion 14 including an impedance coil 15.
  • the coils of the said bell and impeda ce coil can be of any suitable or requisite tesistance. For ordinary work animpedance v coil of say 1000 ohms resistance gives good results, itbeing preferable, however; that the impedance of this coil be higher-than that of the bell-magnet.
  • the winding 8 can be of 600 turns, and the winding 9 may be of 1800 turns.
  • the resistance of the coils 8 and 9 can be suitably adjusted.
  • the coil 8 can be of 9ol1ms-resistance, and the coil 9 can be of 21 ohms resistance.
  • the capacity of the condenser can also vary according to requirements. For example, from c to it may be of s microfarads, and from a to c of two microfarads. These resistances etc. have been tried and found to give very good results.
  • the alpparatusis adapted :Eo'r what are commonly knownas sele mive-telephonet systems.
  • an alternating current "of too high frequency to pass through the impedance coil 15, when projected on to the wire 2 will then pass through the coils of the bell 13. But if such current is of comparatively low frequency, then it may 5 pass through the impedance coil 15, and in such case the bell does not rin
  • the bell 13 will respond to a current of predetermined character, and a current which is projected on to the line for the express pur- 1 pose of ringing this bell, butnot to currents of a decidedly different character, and which may be projected on to the line for the purpose of ringing other bells along the party line.
  • the condenser exeludes battery current from the ringer 13, as well as from'the receiver 7 the latter being excluded from all flow of battery current through the transmitter. "Neither can any battery current flow from the line through the transmitter and receiver to the ringer and then to ground, as the condenser is not only in the parallel path including one winding of the induction coil, but is also directly in the leg to ground through "the ringer.
  • the one condenser is included in two circuits, namely the ringer circuit just described, and the linec'ircuit through the receiver.
  • the receiver circuit includes the two line conductors, the condenser 10,-
  • the transmitter circuit includes the two line conductors l and 2, the transmitter 3, the switchhook 1, the switch contact 6, and the primary transformer winding 9, as illustrated.
  • the side tones 55 usually resulting therefrom are cut down and materially reduced in the receiver, by the combined action of the condenser and transformer.
  • the condenser cuts ott battery current from the receiver and the ringer, and also serves in conjunction with the inductance of the transformer to reduce side tones in the receiver.
  • the improved subscribers telephone apparatus including transmitter, receiver, hook-switch, condenser, induction coil, bell and impedance coil, the bell and impedance coil connectedin parallel, and the condenser serving for both talking and signaling, being in the path of voice currents through the receiver and ringing currents through the bell,
  • the improved subscribers telephone apparatus comprising a bell, an impedance coil connected in parallel with said bell, a three-way condenser having one member thereof connected to ground through the medium of said bell and impedance coil, a telephone receiver, and a path for voice currents including the condenser in series with the telephone receiver.
  • a telephone subscribers apparatus comprising a receiver, a three-way condenser having one member thereof connected to ground, a selectively responsive bell having its coils in said grounded connection and a path for voice currents including the condenser in series withthe telephone receiver.
  • the improved subscribers telephone apparatus including a receiver, a threeway condenser having one' member thereof connected to ground, an impedance coil and the coils of a selective bell connected in said ground connect-ion and a path for voice our rents including the other two members of thecondenser in series with the telephone re- 10.
  • a subscribers telephone apparatus comprising an induct-ion coil having both windings temporarily connected in parallel in the talking circuit, together with a bell l3 and impedance coil 15 connected in parallel in a connection extending between ground and the parallel path of the secondary winding.
  • a telephone circuit having two parallel paths, one of said paths including only a primary transformer winding and the other 'path including a condenser serially connected in circuit with a telephone receiver and the secondary of said transformer, to-
  • a telephone transmission circuit a source of current and a telephone transmitter serially included in the main circuit, an induction coil included in said circuit having a primary and a secondary winding connected in parallel with each other and included serially in-the circuit with said transmitter, one of the parallel branches serially including a condenser and receiver in circuit, together with a bell 13 .and impedance coil 15 connected in parallel to ground through said condenser, and an -impedance element connected in shunt of said ringer.
  • a common battery'telephone system comprising a condenser, 21; subscribersreceiver excluded from the path of battery current by the condenser, an induction coil having its two windings included m paral lel in the talking circuit, a ringer connected to ground through said condenser, and an impedance element connected in shunt of said ringer.
  • a common battery telephone system comprising a condenser, a subscribers receiver excluded from the flow of all common .iattery current by the condenser, aringer connected to receive ringing current through said condenser, and an impedance element connected in shunt only of said ringer.
  • a common battery telephone system comprising a condenser, a subscribers receiver excluded from the path of battery current by the condenser, an induction coil having its two windings included in parallel in the talking circuit, a ringer connected to receive ringing current through said condenser, and an impedance element connected in shunt of said ringer.
  • A' common battery telephone system comprising a condenser, a transformer, a selectively responsive ringer, a receiver connected in series with the secondary of the transformer, 'and in series with the condenser and the selectively responsive ringer.
  • a telephone circuit having two parallel paths, one of said paths including only a primary transformer winding and the other path including a condenser serially connected in circuit with a telephone receiver and the secondary of said transformer, and a selectively operated ringer connected to receive ringing current of the proper frequency through said condenser.
  • a telephone transmission circuit a source of current and a tele phone transmitter serially included in the main circuit, an induction coil included in said circuit having. a primary and a secondary'winding connected in parallel with each other and included serially in the circuit with said transmitter, one of the parallel branches serially including a condenser and receiver in circuit, and a selectively operated ringer connected to receive ringing current of the proper frequency through said condenser.
  • a telephone circuit having two parallel paths, one of said paths including only a primary transformer winding and the other path including a condenser serially connected in circuit with a telephone receiver and the secondary of said tra nsformer, and a ringer and impedance coil in shunt thereof and connected to receive ring- 1ng current through said condenser.
  • a telephone transmission circuit a telephone transmitter serially included in the main circuit, an induction coil included in said circuit having a primary and a secondary winding connected in parallelwith each other and included seriallyin the circuit with said transmitter, one of the parallel branches 'seriallyincluding a condenser and receiver in circuit, and a ringer and impedance coil in shunt thereof and connected to receive ringing current through said condenser.
  • a telephone circuit having two parallel paths, one of said paths including only a primary transformer winding and the other path including a condenser serially connected in circuit with a telephone receiver and the secondary of said transformer, and a selectively responsive ringer connected with a third terminal of said condenser.
  • a telephone transmission circuit a source of current and a telephone transmitter serially included in the main circuit.
  • an induction coil included in said circuit having a primary and a secondary winding connected in parallel with each other and included serially in the circuit with said transmitter, one of the parallel branches serially including a condenser and receiver in circuit, and a selectively responsive ringer connected with a third terminal of said condenser.
  • a receiver a selectively responsive ringer, a condenser interposed between the receiver and ringer, and a line connected with the receiver and ringer through the medium of said condenser, said condenser having a higher capacity for the receiver than for the ringer.

Description

H. P. GLAUSEN.
Y SUBSGRIBERS-TELEPHONE APPARATUS.
APPLICATION FILED MAR.23, 190s.
Patented Dec. 5, 1911."
her of subscribers.
UNITED STATES PATENT OFFICE.
HENRY P. CLAUSEN. OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO STROMBERG-CARLSON TELEPHONE MANUFACTURING COMPANY, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.
SUBSCRIBERS TELEPHONE APPARATUS.
To all whom it may concern:
Be it known that I, Hn-xnr P. CLAUSEN, a citizen of the UnitedStates of America, and resident of Chicago, Cook county, Illinois, have invented a certain new and useful Improvement in Subscribers Telephone Apparatus, of which the following isa specification.
My invention relates to subscribers tele-- and also of such character that side tones or disturbances the receiver will be cut down or eliminated as much as possible. The side-toneless feature of my invention is, however, claimed in my application, Serial Number 147,322, filed March 11, 1903,
and the claims of this patent are, therefore,
limited to the features and combinations not disclosed in said prior application.
To the foregoing and my invention consists in matters hereinafter set forth and claimed.
In the accompanying drawings, the diagram illustrates a subscribers telephone ap- .paratus embodying the principles of my invention.
As thus illustrated, and as thus embodied in practical form, my invention may comprise a pair of line conductors 1 and 2, adapted to serve as a party-line for a num- The apparatus at one of the subscribers stations may be of the character shown in. the diagram. In this diagram the transmitter 3 has one terminal connected with the line wire 1, and its other terminal connected with the hook-switch 4:. The said transmitter and hook-switch may be of any suitable known .or approved construction, the latter, however,
being preferably provided with the two contacts 5 and 6. These contacts are normally opened, but are closed when the receiver 7 is removed from its normal position or resting place upon the saiid hookswitch. As illustrated, the 'receiver' has one terminal connected with the contact 5, and
Specification of Letters Patent.
other useful ends,
Patented Dec. 5, 1911.
Application filedMarch 23, 1903. Serial No. 149,045.
its other terminal connected with one terminal of the winding 8 of the induction coil. The other contact 6 can be connected with one terminal of the other winding 9 of said induction-coil. The other terminals of the windings 8 and 9 are respectively connected with the three-way condenser 10 and I the line-wire 2. The winding 9 is also connected with another part of the said con-- denser through the medium ofthe conductor 11. The third portion of the said condenser is provided with a conductor leading to ground at 12. In this ground connection,
a polarized hell or ringer 13. is located, and around this bell there is preferably a shunt connect-ion 14 including an impedance coil 15. The coils of the said bell and impeda ce coil can be of any suitable or requisite tesistance. For ordinary work animpedance v coil of say 1000 ohms resistance gives good results, itbeing preferable, however; that the impedance of this coil be higher-than that of the bell-magnet. The winding 8 can be of 600 turns, and the winding 9 may be of 1800 turns. The resistance of the coils 8 and 9 can be suitably adjusted. For example, the coil 8 can be of 9ol1ms-resistance, and the coil 9 can be of 21 ohms resistance. The capacity of the condenser can also vary according to requirements. For example, from c to it may be of s microfarads, and from a to c of two microfarads. These resistances etc. have been tried and found to give very good results.
. In operation the novel circuit arrangement particularly of the induction coil, condenser, receiver, and transmitter, tends to prevent disturbances in the receiver during the use of the transmitter, and-to cut down what are commonly-known as side tones. In other words, the arrangement of the instruments appears to give areactionary effect, which, as stated, quiets the circuit and permits the use of the transmitter. without ter, but not to other currents. In. way,
the alpparatusis adapted :Eo'r; what are commonly knownas sele mive-telephonet systems. For example, an alternating current "of too high frequency to pass through the impedance coil 15, when projected on to the wire 2 will then pass through the coils of the bell 13. But if such current is of comparatively low frequency, then it may 5 pass through the impedance coil 15, and in such case the bell does not rin Thus the bell 13 will respond to a current of predetermined character, and a current which is projected on to the line for the express pur- 1 pose of ringing this bell, butnot to currents of a decidedly different character, and which may be projected on to the line for the purpose of ringing other bells along the party line.
It will be seen that the condenser exeludes battery current from the ringer 13, as well as from'the receiver 7 the latter being excluded from all flow of battery current through the transmitter. "Neither can any battery current flow from the line through the transmitter and receiver to the ringer and then to ground, as the condenser is not only in the parallel path including one winding of the induction coil, but isalso directly in the leg to ground through "the ringer.
With such arrangement an alternating cur rent of comparatively high frequency can pass over the line and through the condenser and through the ringer, as it will not pass '30 through the impedance coil 15. A current of lower frequency, however, will pass through the said impedance coil, and thus the bell will not be rung. For the other bells or ringers on the line, any other suitable or desirable provision can be made for making them selectively responsive to their allotted ringing currents. Furthermore, with the arrangement shown the so-called side tones are cut down and modified in the 40 receiver, when. the subscriber uses his transmitter. At the same time voice currents are efiiciently received in the receiver from the other end of the circuit.
In operation the ringing current, of suitable frequency, comes over the line wire 2,
thence over the conductor 11 to the condenser, through the condenser 10 to the ringer 13, and then to'ground at-12. The ringing current does not pass through the impedance coil 15, because the retardation thereof is too great for the frequency employed. Thus the one condenser is included in two circuits, namely the ringer circuit just described, and the linec'ircuit through the receiver. The receiver circuit includes the two line conductors, the condenser 10,-
the secondary transformer winding 8, the receiver 7, the contact point 5 and switchhook 4, and the transmitter '3. The transmitter circuit includes the two line conductors l and 2, the transmitter 3, the switchhook 1, the switch contact 6, and the primary transformer winding 9, as illustrated. During use of the transmitter, the side tones 55 usually resulting therefrom are cut down and materially reduced in the receiver, by the combined action of the condenser and transformer. The condenser cuts ott battery current from the receiver and the ringer, and also serves in conjunction with the inductance of the transformer to reduce side tones in the receiver.
I claim as my invention:
1. The combination of a subscribcrs telephone line, a transmitter having one tcrn'iinal connected with one side of the line, a hook-switch connected with the other terminal of the transmitter, said hook-switch having two normally open contacts, an induction-coil having one terminal of its primary coil connected with the other side of the line, and its other terminal connected with one of said contacts, a receiver having one of its terminals connected with thcother of said contacts, and its other terminal con nected with one terminal of the secondary winding of said induction-coiha threeway condenser connected with the other terminal of the secondary winding of the induction coil, said condenser being also connected with the terminal of the primary winding which is connected to one side of the line, a ground connection extending from said condenser, an electric bell having its magnet. coils located in said ground connection, and an impedance coil located in a shunt connection extending around said magnet coils.
9. The combination of a subscribers telephone line, a. transmitter and a hook-switch and the primary winding of an induction coil connected in a normally open bridge across the line, said bridge being normally open at the hook-switch, a normally-open parallel connection extending around said primary winding, said parallel connection being normally open at the. hook-switch, and said parallel connection including a coin denser and the secondary winding oi said induction-coil. and a receiver, the said secondary winding being located between the receiver and the condenser, a ground eonnection extending from said condenser, an electro-magnet signaling device having its coils located in said ground connection, and an impedance coil located in a shunt extending around said signaling device.
3. The combination of a complete metallic line circuit, a suitable transmitte' and receiver, av suitable hook-switch and inductioncoil, a three-way condense and a signaling device and an impedance coil connected in parallel and located in a conductor extending from said condenser to ground, and suitable connections whereby the closing of said switch places the transmitter, the receiver, the secondary winding of the induction-coil, and the condenser in a bridge extending across the circuit, and whereby such action of the switch also operates to place the primary winding of the induction coil in a parallel connection extending around the condenser and receiver.
4. The combination of a subscribers line, a condenser connected with the line, a. bell having its coils located in a conductor extending from said condenser to ground, an impedance coil located in a parallel connec-' tionextendingar and said bell, said impedance coil being r higher impedance than the bell magnets, a hook-switch with two normally open contacts, a transmitter and a receiver, a suitable induction-coil, suitable connections whereby the closing of said switch-contacts places the transmitter, the receiver and the secondary winding of said induction coil in a bridge across the talking circuit, said bridge including -suitable ca pacity, and whereby such action on the part of said switch also operates to place the primary winding of the induction coil in a parallel connection extending around said condenser and receiver.
5; The improved subscribers telephone apparatus, including transmitter, receiver, hook-switch, condenser, induction coil, bell and impedance coil, the bell and impedance coil connectedin parallel, and the condenser serving for both talking and signaling, being in the path of voice currents through the receiver and ringing currents through the bell,
' all organized substantially as shown and described.
6. The improved subscribers telephone apparatus comprising a bell, an impedance coil connected in parallel with said bell, a three-way condenser having one member thereof connected to ground through the medium of said bell and impedance coil, a telephone receiver, and a path for voice currents including the condenser in series with the telephone receiver.
7. A telephone subscribers apparatus comprising a receiver, a three-way condenser having one member thereof connected to ground, a selectively responsive bell having its coils in said grounded connection and a path for voice currents including the condenser in series withthe telephone receiver.
8. The improved subscribers telephone apparatus, including a receiver, a threeway condenser having one' member thereof connected to ground, an impedance coil and the coils of a selective bell connected in said ground connect-ion and a path for voice our rents including the other two members of thecondenser in series with the telephone re- 10. A subscribers telephone circuit, com-' prising it condenser, a receiver, an impedance coil andan electric bell, the receiver being grounded I through the condenser in series with the bell and impedance coil in parallel.
11. A subscribers telephone apparatus comprising an induct-ion coil having both windings temporarily connected in parallel in the talking circuit, together with a bell l3 and impedance coil 15 connected in parallel in a connection extending between ground and the parallel path of the secondary winding.
12. In combination, a telephone circuit, a source of current and a transmitter in said circuit, the primary of a transformer in said circuit, and a condenser and the secondary of said transformer serially connected in shunt only of said primary winding, together with.
a bell 13 and impedance coil 15 connected in parallel in a connection extending between ground and the parallel path of the sec ondary. I
13. A telephone circuit having two parallel paths, one of said paths including only a primary transformer winding and the other 'path including a condenser serially connected in circuit with a telephone receiver and the secondary of said transformer, to-
gether with? bell 13 and impedance coil 15 connected in parallel in a connection extending bet-ween ground and the parallel path of the secondary.
1 1. In combination, a telephone transmission circuit, a source of current and a telephone transmitter serially included in the main circuit, an induction coil included in said circuit having a primary and a secondary winding connected in parallel with each other and included serially in-the circuit with said transmitter, one of the parallel branches serially including a condenser and receiver in circuit, together with a bell 13 .and impedance coil 15 connected in parallel to ground through said condenser, and an -impedance element connected in shunt of said ringer. I
17. A common battery'telephone system comprising a condenser, 21; subscribersreceiver excluded from the path of battery current by the condenser, an induction coil having its two windings included m paral lel in the talking circuit, a ringer connected to ground through said condenser, and an impedance element connected in shunt of said ringer.
18. A common battery telephone system comprising a condenser, a subscribers receiver excluded from the flow of all common .iattery current by the condenser, aringer connected to receive ringing current through said condenser, and an impedance element connected in shunt only of said ringer.
19. A common battery telephone system comprising a condenser, a subscribers receiver excluded from the path of battery current by the condenser, an induction coil having its two windings included in parallel in the talking circuit, a ringer connected to receive ringing current through said condenser, and an impedance element connected in shunt of said ringer.
20. A' common battery telephone system comprising a condenser, a transformer, a selectively responsive ringer, a receiver connected in series with the secondary of the transformer, 'and in series with the condenser and the selectively responsive ringer.
21. A telephone circuit having two parallel paths, one of said paths including only a primary transformer winding and the other path including a condenser serially connected in circuit with a telephone receiver and the secondary of said transformer, and a selectively operated ringer connected to receive ringing current of the proper frequency through said condenser.
22. In combination, a telephone transmission circuit, a source of current and a tele phone transmitter serially included in the main circuit, an induction coil included in said circuit having. a primary and a secondary'winding connected in parallel with each other and included serially in the circuit with said transmitter, one of the parallel branches serially including a condenser and receiver in circuit, and a selectively operated ringer connected to receive ringing current of the proper frequency through said condenser.
23. A telephone circuit having two parallel paths, one of said paths including only a primary transformer winding and the other path including a condenser serially connected in circuit with a telephone receiver and the secondary of said tra nsformer, and a ringer and impedance coil in shunt thereof and connected to receive ring- 1ng current through said condenser.
24. In combination, a telephone transmission circuit, a telephone transmitter serially included in the main circuit, an induction coil included in said circuit having a primary and a secondary winding connected in parallelwith each other and included seriallyin the circuit with said transmitter, one of the parallel branches 'seriallyincluding a condenser and receiver in circuit, and a ringer and impedance coil in shunt thereof and connected to receive ringing current through said condenser.
25. A telephone circuit having two parallel paths, one of said paths including only a primary transformer winding and the other path including a condenser serially connected in circuit with a telephone receiver and the secondary of said transformer, and a selectively responsive ringer connected with a third terminal of said condenser. v I
26. In combination, a telephone transmission circuit. a source of current and a telephone transmitter serially included in the main circuit. an induction coil included in said circuit having a primary and a secondary winding connected in parallel with each other and included serially in the circuit with said transmitter, one of the parallel branches serially including a condenser and receiver in circuit, and a selectively responsive ringer connected with a third terminal of said condenser.
27. A. receiver, a selectively responsive ringer, a condenser interposed between the receiver and ringer, and a line connected with the receiver and ringer through the medium of said condenser.
28. A receiver, a selectively responsive ringer, a condenser interposed between the receiver and ringer, and a line connected with the receiver and ringer through the medium of said condenser, said condenser having a higher capacity for the receiver than for the ringer.
Signed by me at Chicago, Cook county, Illinois. this 17th day of March, 1903.
HENRY P. OLAUSEN.
Witnesses:
A. F. DURAND, WM. A. HARDERS.
US14904503A 1903-03-23 1903-03-23 Subscriber's telephone apparatus. Expired - Lifetime US1010478A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US14904503A US1010478A (en) 1903-03-23 1903-03-23 Subscriber's telephone apparatus.

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US14904503A US1010478A (en) 1903-03-23 1903-03-23 Subscriber's telephone apparatus.

Publications (1)

Publication Number Publication Date
US1010478A true US1010478A (en) 1911-12-05

Family

ID=3078788

Family Applications (1)

Application Number Title Priority Date Filing Date
US14904503A Expired - Lifetime US1010478A (en) 1903-03-23 1903-03-23 Subscriber's telephone apparatus.

Country Status (1)

Country Link
US (1) US1010478A (en)

Similar Documents

Publication Publication Date Title
US1010478A (en) Subscriber's telephone apparatus.
US3617645A (en) Signaling circuit with audible noise reduction
USRE15070E (en) of chicago
US2584830A (en) Telephone substation equipment with variable antisidetone circuit
US2344338A (en) Substation circuit
US1657634A (en) Substation telephone circuits
US1484396A (en) Telephone system
US2134690A (en) Electrical communication network
US1424368A (en) Substation telephone circuits
US1517382A (en) Substation circuit
US2134691A (en) Electric communication network
US3068325A (en) Telephone sub-stations including transistors
US2332551A (en) Telephone set circuit
US2232398A (en) Telephone substation circuit
US1688475A (en) Substation telephone circuits
US3345467A (en) Telephone systems and apparatus
US797761A (en) Composite telegraph and telephone system.
US901738A (en) Subscriber's telephone-circuit.
US1035158A (en) Telephone apparatus.
US1636330A (en) Substation telephone circuit
US492482A (en) Signaling apparatus and circuit
US553605A (en) Composite telegraphic and telephonic transmission
US1901958A (en) Substation circuit
US2912512A (en) Anti-sidetone and line balancing telephone circuit
US1664468A (en) Program-selecting circuits