US1391006A - Half-duplex alternating-current telegraph system - Google Patents

Description

R. D. PARKER.

HALF DUPLEX ALTERNATING CURRENT TELEGRAPH SYSTEM.

APPLICATION FILED SEPT-8. I919.

Patented Sept. 20,1921.

INVENTOR. fiflfimer lllllllllll A TTORNEY UNITED STATES PATENT OFFICE.-

narlznmonn n. manna, or BROOKLYN, new YORK, ASSIGNOR 'ro AMERICAN mamrnoun AND TELEGRAPH COMPANY, A CORPORATION or NEW YORK.

nALr-nurnnx AL'rnnimrmo-cunmr TELEGRAPH srsrmr.

To all whom it my concern:

Be it known that I, 'RALZEMOND D. PARKER, residing at Brooklyn, in the county of Kings and State of New York, have invented cer- 5.tain Im rovements in Half-Duplex Alternatingurrent Telegraph Systems, of which the following is a specification.

This inventionrelates to signaling circuits and more particularly to telephone lines composited for Morse or other telegraph operation, and provided with arrangement for superposing carrier current signaling channels thereon.

One of the principal features of this invention resides in the provision of an alternating current signaling channel for. a

transmission line, so arranged as to be operated upon a half duplex basis by means of standard telegraph equipment such as is 'now used for transmitting Morse signals.

Other and further features of the invention will be more 'fullyunderstood from the following description when read in connection with the accompanying drawing, the

figure of which illustrates a circuit diagram embodying one form of the invention:

In the diagram ML designates a telephone transmission line rovided with composite apparatus CX at its terminal station, for

superposing Morse signals upon the line.

The composite apparatus is of the usual and -we ll-lmown form and need not be described herein. In order to provide an alternating carrier current signaling channel, a tuned branch TBis bri ged across the mainline ML, said tuned branchhaving associated therewith a carrier circuit, CC, coupled thereto through the transformer 1. Included in said carrier circuit CC are the four windings 10, 11, 12 and 13,,gof a differential alternating current receiving relay DR. A transmitting circuit TC is bridged across the midpoints of the-windings of the differential relay DR, so that-by the provision of a balancing artificial line or network MN energy from the transmitting circuit TC will not efiect the receiving-relay DR. The transmitting circuit T'C includes an alternating current generator G and a contact controlled by. the armature of the relayPR, which may be the standard pole changing relay employed in half duplex Morse systems. As is well understood, this pole changing relay includes a main coil 2 inserted in the loop extending to the sub- Speciflcation of Letters Patent.

Patented se t. 20, 1921.

Application filed September 8, 1919. Serial No. 322,268.

' scribers oflice and an auxiliary coil 3 controlled by a receiving relay RR in such a manner as to prevent the armature of the relay PR from opening the sending circuit TC in response to received signals. The relay RR is of course controlled by the differentlal receiving relay DR. The relay RR is arranged to open and close the loo extending to thesubscribers ofiice, whic loop contains a key K and a relay 4 for operating a sounder S at the subscribers office. At the main terminal station a V sending key K is provided for use by the operator at suchstation, and a sounder S 1s also provided at said station, the sounder 7 being controlled by the armature of the pole changing relay PR.

Further details of the apparatus may now be understood from the operation which is as follows:

Signals may be transmitted either by operating the key K at the subscribers oflice,

or by operating the key K at the main termlnal stat on. When the subscribers loop 1s opened in response to either of these operat1ons,- the coil 2 of the pole changin relay is cle'e'nergized. Since the relay R is normally energized by current applied through the resistance 5, the coil 3 of the pole changin relay PR is normally shortcircuited by t he ground connection over the contact 6 of the relay RR consequently the opening of the subscribers loop causes the armature of thepolechanging relay PR 'to fall off andopen the transmitting circuit TC, at the same time actuating the sounder S The sounder S at the subscribers'ofiice is operated-by the opening of the subscribers loop. In the normal condition of the cir cuit, alternating current ener is transmitted through the generator from the circuit TC to the midpoints of the windings of the differential relay DR. This energy. divides between the artificial line MN and v the transformer 1', withoutaflecting the re- 100 lay DR. From the transformer 1 the alternating current energy is transmitted. through the tuned branch TB and over the main line ML to the distant station. The interruption .of current from the generator .105 G by the opening of the circuit TC, just described, actuates the receiving apparatus at the distant station. v

The operation of the receiving apparatus at the distant statlon, which i similar to110 that illustrated in Fig. 1, may be understood from a description of the operation taking place at the station of Fig. 1, in response to signals received from the. distant station. Normall alternating current is then received rom the distant station .over the main line ML, said alternating current being selected by the tuned branch TB and transmitted through the transformer 1 to the circuit CC. This energy flows seriall through the four windings of the relay D thereby holding its armature to the left, as shown in therefore deenergized and by opening con the drawing. As soon a this received alternating current energy is interrupted by the actuation of a key at the distant station, the

armature of the relay DR is drawn to the right by a spring and the relay BB is shortcircuited by the ground connection over the make contact of the relay DR. Relay BB is tact 6 removes the short-circuit from about coil 3 of the pole changing relay, so that said relay is energized to hold up the armature of the pole changing relay. At the same time the contact 7 of relay RR is opened,

thereby opening the subscribers loop to actuate the sounder S at the local subscribers' office. This also results in opening the circuit of the coil 2 of the pole changing 7 relay PR, but since, as just described, the

' signal back to the sending station.

coil 3 is at the same time energized, the pole changing relay does not respond to the received signal to actuate the transmitting circuit TC and cannot transmit the sarrfie e sounder S does not res 0nd to received signals, but is merely for t e purpose of checking transmitted signals. v

t will be obvious that the general principles herein disclosed may be embodied in ceiving relay, a pole changing relay responsive to said key, for controlling said carrier currents, and means to prevent the actuation of said. pole changing relay by said receiving relay, in response to received signals.

2. In a signaling system, a transmission line, means to signal over said line by carrier currents comprising a differential receiving relay, a source of carrier current signaling energy so arranged that energy may be transmitted to the line, without afiecting said difl'erential receiving relay, a normally closed subscribers loop, a sending key therein, and a sounder associated with said loop, means whereby said difl'erential .receiving relay, in response to received signals, may open said loop to actuate said sounder, a pole changing relay associated with said loop in such a manner as to be responsive to said sending key,-said pole changing relay operating to control the transmission of carrier current energy from said carrier source to said transmission line, and means to prevent the actuation of said pole changin relay when the subscribers loop is opened y said receiving relay to actuate the sounder associated with said loop.

'3. In a ignaling system, a transmission line, means to signal over said line by carrier currents comprising a differential receiving relay, a source-ofl carrier current signalmg energy so arranged that energy may be transmitted to the line without afiecting said difi'erential receiving relay, a normally closed subscribers loop, a sending key therein and a sounder associated with said loop, means whereby said difl'erential receiving relay in response to received signals may open said loop to actuate said sounder, a pole changing relay having one coil in said subscribers' loop, whereby said pole changing rela in response to the actuation of said sen ing key may control the transmission of carrier current energy from said carrier source to said transmission line, and a locking coil for said pole changing relay, having its circuit so arranged that said relay is energized under the control of the difierential receiving relay when said differential receiving relay opens the subscribers loop to actuate the sounder associated therewith.

In testimony whereof, I have signed my name to this specification this 5th day of September, 1919.

- RALZEMOND D. PARKER.

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