DE1044867B - Circuit arrangement for connecting a single-current local line to a telegraph line with separate transmission and reception channels, especially for AC telegraphy systems - Google Patents

Description

With Telegrane long-distance connections is known full duplex operation is common. In this operating mode, the signals are simultaneously in both Directions given over the connecting line. The local line between a telegraph office and the The end point of the long-distance line generally consists of a single-flow line which, depending on the symbol in the is open or closed. In this case, the transmission can take place during a period of time can only ever be done in one direction. For this reason, it is desirable that the receptionist be at End of the line can give the broadcast operator a message that he wants to join the connection. To the Various solutions have already been proposed to realize this possibility. It is Z. B. known to switch on an additional relay, called "interrupt relay", in series in the local line in each terminus.

In the case of carrier telegraphy systems that work via long-distance lines, the desired transmission relay usually replaced by a telegraphy module. In order to create the possibility of interruption, it is known to use the single-current local line with a conversion circuit to be provided at the end station, this conversion circuit a transmission relay and a Includes interrupt relay. So two special relays were necessary for each local line. These Switching is therefore very complex and causes additional interference.

The invention relates to a circuit arrangement for connecting a local line operated with single current to a telegraph line with separate transmitting and receiving channels, in particular for alternating current telegraphy systems. The disadvantages underlying the known arrangements of this type are avoided according to the invention in that a constant current flows from a battery separate from the local battery in the input circuit of the transmission channel, on which a part of the local current controlled by the local battery, controlled by the reception signals, is superimposed in this way is that when the local line is closed, regardless of the characters received, a character stream flows in the input circuit of the transmission channel, while when the local line is interrupted in the transmission channel, depending on the characters received, character and separating current flows alternately. According to a further embodiment of the invention, the additional battery is expediently located in one diagonal of a Wheatstone bridge, one of which is branched from Ί «.τη. ^ Starting circle of the transmission channel is formed. The local line and the movable changeover contact of a polarized receiving relay are connected to the two other diagonal points of the bridge. This receiving relay controls the local current in the circuit arrangement for connection

a single current local line to a

Telegraph line with separate transmit and receive channels, especially for AC telegraphic systems

Applicant:

International Standard Electric
Corporation, New York, NY (V. St. A.)

Representative: Dipl.-Ing. H. Ciaessen, patent attorney,
Stuttgart-Zuffenhausen, Hellmut-Hirth-Str. 42

Claimed priority:
Great Britain 13 September 1955

Edward A. Foulkes, William F. S. Chittleburgh

and Seibor C. Dziembowski, London,

have been named as inventors

Way that when receiving separation steps only the additional current flowing in the direction of the character in the input circuit is present and when receiving character steps with a closed local line a part of the local current in the same direction as the additional current; when the local line is open, part of the local current that is greater than the additional current in the opposite direction Direction of how the additional current flows in the input circuit.

In the drawing, a circuit arrangement according to the invention is shown. A terminus 1 a telegraphy long-distance connection is with a local office 2 via a single-stream local line 3 tied together. The local office 2 is represented by a teleprinter, of which only the receiving coil 4, the send contact 5 and the grounded negative telegraph battery 6 are drawn. The receiving coil 4 is connected to the local line 3 via the normally closed contact of a switch 29 connected.

The end station 1 contains a transmit telegraphy modulator 7 and a reception telegraphy demodulator 8, which are connected to the corresponding transmission and reception channels 9 and 10 of the long-distance line are connected. The 'demodulator 8 controls a polarized one

1809 680/213

Receiving relay 11, its sign or isolating contact 12 or 13 connected to the corresponding positive or negative terminal of the conventional telegraph battery 14 is. The center of the battery is grounded. The movable spring 15 of the relay 11 is connected to the local line 3 via two resistors connected in series 16, 17 connected. The resistor 17 is variable.

The input circuit of the modulator 7 forms one arm of the balanced Wheatstone bridge 18, the other three bridge arms contain the resistors 19, 20 and 21. A pair of the diagonal end points 22, 23 is connected in series with a resistor 24. Resistor 16 is parallel to this arrangement. Digonal end points 25 and 26 are connected to the positive and negative terminals, respectively, of a direct current battery 27 which is separate from telegraph battery 14. The end point 23 is connected to the negative terminal of the battery 14 via an adjustable resistor 28. When the bridge is balanced, no current can flow from the battery 27 in the circuit connected to the endpoints 22 and 23 and vice versa. The battery 27 supplies a current component I ₁ to the modulator 7 in the direction from the end point 25 to the end point 22. If a sufficiently large current flows in this direction via the modulator 7, the line 9 receives symbol current. If the current flows in the opposite direction, the line is in the disconnected state, as shown by the two arrows M and 5 ″. The current components in these directions are called symbol or discrete current components.

If the receiving relay 11 is in the drawing state, as shown in the drawing, it is at the bottom At the end of the resistor 16 a positive potential, and a current flows from the station 1 to the local office 2 via the local line 3, whereby the teletypewriter (represented by 4, 5) is stopped.

The resistors 24 and 28 form a voltage divider which is connected in parallel to the battery 14. The magnitude and direction of the potential delivered to endpoint 23 depends on the relative magnitudes of these two resistances. Resistor 24 should be selected to be smaller than resistor 28, so that a positive potential to earth reaches end point 23 and thus an additional current component I _{2 flows} in the direction of the drawing, ie direction M via modulator 7. The total character stream is then / ^ = J _{1 -JJ 2} .

If the receiving relay 11 switches to the disconnected state, a negative potential is applied to the end point 23, and the resistors 24 and 28 are in parallel. A negative potential is also fed to line 3 via resistor 17. If the battery 6 supplies a negative isolating potential which is equal to the negative or isolating potential of the battery 14, no current flows from the battery 14 in the bridge 18 or in the line 3. The teletypewriter starts up and through the modulator 7 Only the symbol stream component I _{1 flows} . As long as I _{1 is} so large that the modulator 7 holds the line 9 in the character state, this line is not influenced by the signals received via the line 10.

For the following consideration it should be assumed that the relay 11 is in the character state and the movable contact 15 is in the position shown and furthermore that the transmission contact 5 of the teleprinter in the local office 2 is opened. In this case, the current in the local line 3 becomes zero. The end point 22 is therefore positive with respect to the end point 23 because of the voltage divider 24, 28. An isolating current component I ₃ therefore flows via the modulator 7. The total separation current is therefore I ₅ = J ₃ -Z ₁ . The resistances should of course be chosen so that I _{3 is} greater than I ₁ . It is also useful to choose Im ⁼ Is or I ₃ = 2I ₁ + J ₂ . This gives the line 9 the disconnected state, since the current flows through the modulator 7 as desired in the corresponding direction.

If the relay 11 switches to the disconnected state while the contact 5 is open, both end points 22 and 23 are connected to the same terminal of the battery 14, and therefore no current can flow in the bridge from this battery. The separating current component I ₃ becomes zero, and only the symbol component J ₁ flows through the modulator, and the line 9 is in the symbol state.

If the contact 5 in the local office 2 is open and the movable contact 15 is on contact 12, an isolating current J _{5 is} fed to the modulator 7, and if it is closed, a character current I _{M will} flow in the modulator 7 instead, see above · That the corresponding separator and character signals are sent in the desired manner.

It is now assumed that signals are received and the officer of the local office 2, z. B. by the switch 29, the line 3 has opened. As already explained, an isolating current J _{5 is} fed to the modulator 7 when the local line 3 is open and when the movable contact 15 of the relay 11 has switched ^{to character state 1.} If the receiving relay 11 now switches over, the separating _{current component J 3} becomes zero, and only the current component J _{1 flows} from the battery 27 via the modulator 7, which, as already described, is in the drawing state. From this it can be seen that when the receptionist in the end office 2 opens the local line 3, the transmission official receives the signals sent by himself. From this he can immediately see that the receptionist has interrupted.

Claims (3)

Patent claims: 1. Circuit arrangement for connecting a local line operated with single current to a Telegraph line with separate transmit and receive channels, especially for AC telegraph systems, characterized in that one is separated from the local battery (14) Battery (27) a constant current in the input circuit (7) of the transmission channel (9) flows, which is a part of the local current from the local battery (14) controlled by the received signals in this way it is superimposed that when the local line (3) is closed, regardless of the characters received Character stream in the input circuit (7) of the transmission channel (9) flows, while in the event of an interrupted local line (3) in the transmission channel as a function of the received characters alternately character and separator current flows. 2. Circuit arrangement according to claim 1, characterized in that the additional battery (27) is connected to two diagonal points of a balanced Wheatstone bridge (18), one branch of which is formed by the input circuit (7) of the transmission channel (9) that the two other diagonal points between the changeover contact (15) of the polarized receiving relay (11) and: the Qrtsleitung (3) are switched, and that the receiving relay (11) the local current in the Way controls that when receiving separation only the additional current flowing in the direction of the characters stepped is present in the input circuit (7) and when receiving character steps with closed Local line (3) a part of the local current in the same direction as the additional current, when open Local line (3) a part of the local current, which is greater than the additional current, in the opposite direction .Direction of how the additional current flows in the input circuit (7). 3. Circuit arrangement according to claim 1 and 2, characterized in that between the movable Spring (15) and the isolating contact (13) of the receiving relay connected to the battery a voltage divider is located, the tap of which is connected to a bridge point (23). and that the other Bridge point (22) also placed on the movable contact (15) via a resistor (16) is. 1 sheet of drawings