US2123232A - Telegraph signal repeater - Google Patents

Description

Patented July 12, 193s UNITED srl-tres PATENT OFFICE TELEGRAPH SIGNAL REPEATER Application August 30,

13 Claims.

t inactive relay from being operated by line discharges when used with long cable line circuits.

Another object is to provide a repeater of simple design which may be effectively operated in conjunction with any one of a plurality oi lines of greatly diiering characteristics.

Another object is to simplify the switching of repeaters of this type by an arrangement of the parts such that the adjustment oi the repeater for operation with lines of different characteristics is confined to a single instrumentality, such as a resistance for adjusting the line current.

The present day tendency is to interconnect telegraph subscribers through switchboards which are equipped with repeaters which are individual to the lines or loops and with other repeaters, such as cord circuit repeaters, which must be adapted for use with lines of greatly differing characteristics. The tendency is, furthermore, to use longer and longer subscribers loop cir cuits and to include the conductors for such loops in cables, so that their capacity to ground becomes quite appreciable. The tendency is, furthermore, toward Ahigher speed of transmission.

For these reasons, it is important that repeaters should require as few .adjustments as possible for their proper operation with lines of different characteristics. This is, of course, essential particularly with cord circuit repeaters, which may be connected to long cable lines 0r to open wire lines, but it is also important in connection with repeaters permanently associated with their loops in order to eliminate the continual balance adjustments which hitherto have been necessary in interconnecting subscribers loops.

It is also important that the tendency of line discharges to kick-ofi the inactive relay be obviated and, whereas various ways of accomplishing this object have already been proposed, the general objection to those arrangements is that they ordinarily affect the bias and introduce distortion of the signals.

In accordance with a feature of the invention, the sending relay of a telegraph repeater is connected to transmit directly into the line side of the outgoing circuit and the inactive receiving relay has its line winding connected to the return side of the outgoing circuit, thereby prac- 1935, Serial No. 38,526

tically entirely preventing the line discharges from passing through the inactive relay and eliminating the insertion of anti-kick-of circuit elements.

In accordance with another feature of the in* vention, phase equalizing means are provided in connection with one or the other, or both, of the line and secondary windings of the receiving reu lay. The object of this is to compensate for delay of the impulses through the line winding due to their passage over both sides of the line circuit in series and thus prevent the receiving relay from operating during sending. 'Ihe elements of the phase-equalizing means may be standardized and may be given suitable values for any line circuits which may be encountered in commercial operation. This phase equalizing means may be in the form of a resistance capaci tance network for advancing the phase of outgoing impulses through the line winding of the receiving relay; or in the form of an inductance for retarding the impulses through the balancing winding of the receiving relay; or it may combine both of these arrangements.

In accordance with still a further feature of the invention, a variable line current control impedance is inserted in the line side of the line circuit and the balancing network is reduced to consist only of a fixed resistance of a value suitable for all line circuits which may be encountered in commercial operations.

The invention will now be described in connection with the attached drawing which shows diagrammatically a circuit arrangement for a telegraph signal repeater embodying the various features of the invention. Only so much of the repeater circuit is shown as is directly associated with a line or loop leading to the distant subscribers station.

The repeater station Ris connected over a pair line which consequently will `have mutual disl,

tributed capacity, represented by condensers H4 and l5, and which will have distributed capacities towardthe cable sheath which is grounded, which capacities are represented by condensers ||0, ||2 and ||3.

The repeater station R comprises a transmitting relay which may be operated in any desirable manner either from a local source or from a distant station which may be similar to the station S. Relay |0| has its armature connected directly to the outgoing line conductor |08 and in its marking and spacing positions applies alternately positive and negative potential, respectively, to that conductor. The receiving relay |02 has its armature and contacts connected in any desirable manner for repeating signals into a local circuit or into a line circuit similar to the line |08 and |09. Relay |02 has a line winding connected from the source of negative potential to the return conductor |l9 for reception of signals from station S. This relay also has a second or balancing winding connected from the armature of relay |0| through balancing resistance 01 to ground.

With the circuit in normal position as shown in the drawing, current from the source of positive potential is supplied over marking contact of relay |0| directly to conductor |08 maintaining a positive charge on Condensers IIE! and lll, the current continues through the subscribers station S over conductor |09 through the line winding of relay |02 to negative potential. The condensers ||2 and 3 consequently are normally charged to a negative potential. Condensers Il!! and I| 5 will normally be charged between the positive and negative potentials applied to the two line conductors.

Another circuit may be traced from positive potential over the marking contact of relay |0| through the biasing winding of relay 02 and resistance |07 to ground. The current through the first circuit, and thus in the line winding of relay |02, is in a direction to hold the relay in marking position and is approximately twice the current in the second circuit through the biasing Winding of relay |02, which is in a direction to tend to operate the relay 02 to its spacing position. When the line circuit is opened at subscribers station S for transmission of signals to the repeater station the line circuit including line winding of relay |02 becomes currentless. Relay |02 consequently responds by operating to spacing for the duration of the opening of the line circuit. During such a spacing impulse the charges on line Condensers ||0, HI, H2, H3, H4 and H5 remain practically unaltered.

Again assuming normal condition of the circuit and that a spacing signal is to be transmitted by operation of relay I0! to its spacing contact, negative or spacing potential will then be applied directly to conductor |08. The subscribers station consequently will be practically currentless and thus responds to the spacing impulse, and both line conductors will be connected to spacing potential. The condensers |52 and ||3 consequently remain practically unalected, whereas the charge on Condensers H0 and will be reversed, with the result that very little charging current will flow through the line winding |02 over conductor |09 due to the grounded capacities, and that a comparatively heavy charging current will flow over the line conductor |08. The charges on Condensers IM and H5 will be reduced to Zero, and this small surge will appear in both line conductors, however without appreciable eiect on the relay |02 or the receiving equipment at substation S. With relay |0| in spacing position negative potential is also applied to the biasing winding of relay |02 in a direction the reverse of the previous condition and relay |02 remains in marking position during the spacing impulse. When relay |0| returns to its marking position the charges on Condensers H0 and Ill will again be reversed and current will again flow through the subscribers station, which thus responds to the marking impulse. The mutual capacities |54 and ||5 will again be charged up to nearly full line potential, but this surge is too small to appreciably aiect relay |02. Current will also flow in the line winding of relay |02 and the opposing current in the biasing winding will be reestablished. Thus relay |02 will respond to impulses produced by opening of the line at the subscribers station, but will not respond to impulses produced by reversing the potentials to the line circuit by transmitting relay |0.

From this description it is clear that the comparatively large current surges due to the ground capacity of the line conductors |03 and |09 do not aiect receiving relay |02,

In order that a repeater of this type may be used with diiierent lines, it is necessary to provide means for adjusting the line current. For this purpose variable resistance |03 is inserted in the outgoing line conductor |08. With the line winding of relay |02 in the other conductor the presence of resistance |03 in the outgoing conductor will not delay the decay of current through the line winding of relay |02 when a spacing signal is transmitted from the subscribers station and thus will cause very little distortion.

Inasmuch as relay |02 is practically unaffected by the static conditions on the line circuit it is evident that the articial line |07 need not be arranged to balance such static condition; it may therefore be made of a simple resistance of a value which may be suitable for nearly all loop circuits that may be encountered in commercial plants.

In view of the fact that the line impulses from the contacts of relay lei must rst pass through the line circuit and the distant subscriber station before they reach the line winding of relay |02, the impulses through the local circuit including the balancing winding of relay |02 will reach the biasing winding before the line impulses reach the line winding. Whereas this is satisfactory when relay IGI operates to spacing, the reversal of the current in the biasing winding of relay |02 before a marking impulse arrives in the line winding may cause the relay to kick-off.

This phase relation may be compensated for in dierent ways; thus by means of a capacitance network |0E connected across the outgoing line a marking impulse may quickly be transmitted to the line winding of. the relay |02 and thus prevent the biasing winding from operating the relay to spacing. A similar eiect may be obtained by introducing inductance |05 in the local circuit for the biasing winding of relay |02 thereby delaying the arrival of a reverse impulse through that biasing winding suiiiccntly to permit the marking impulse to arrive iirst in the line winding of relay |02. It is of course possible to use both of these arrangements simultaneously as shown in the drawing. It will, however, be found that a network comprising a single resistance and capacitance bridge |06 will be suflicient; a capacity of 2 microfarads in series with an 3,000 ohm resistance has been found to give satisfactory average operation. In some cases it may be desirable to add a similar resistance-capacitance bridge of a diierent time constant for the purpose of improving the wave shape.

It has been found that the phase correcting means have no distorting effect upon the signals in either direction and the system has the advantage of not requiring devices for preventing kickoff inserted in the line circuit proper, which devices will usually have the effect of introducing bias.

It may be noted that the mutual distributed capacity between conductors |08 and |09 represented by condensers ||4 and ||5 would aid in correcting the phase relation between the irnpulses through the two windings of relay |02.

From the description given above it is apparent that all parts of the repeater circuit may be standardized for permanent use with any line circuit that may be encountered in a commercial plant or for use as a cord circuit repeater for connection with any type of line circuit. The only adjustable device in this arrangement is the line resistance |03. It is thus possible to standardize the equipment to a high degree and also to obtain the necessary flexibility for switchboard operation.

For a complete system extending from the subscribers station S to another similar subscribers station the entire system shown in the drawing, except relays |0| and |02, may be duplicated. Contacts S and M of relay |02 would constitute sending contacts for the other line circuit corresponding to the contacts of relay lill; one winding of relay |0| would be connected to the incoming line and the other winding would be included in a biasing circuit similar to that including the lower Winding of relay |02 and resistance What is claimed is:

1. A two-wire circuit having capacity to ground and having a line side and a return side, signal transmitting means connected to said line side Afor charging said line side alternately to two different potentials with respect to ground, polar receiving relay means having a winding, and a source of potential permanently connected through said windingvto said return side.

2. A telegraph signal repeater operating into an outgoing two-wire line circuit having capacitance to ground, comprising a transmitting relay having contacts for applying alternate potentials to one wire of said line circuit, a receiving relay having an operating winding, a source of potential equal to one of. said alternate potentials connected through said winding to the other wire of said line circuit.

3. A two-wire circuit having capacity to ground and having a line side and a return side, signal repeating means comprising transmitting means connected to said line side for charging said line side alternately to positive and negative potentials with respect to ground, a iixed potential connected to said return side, and a polar receiving relay having a winding connected in said return side to be substantially unaffected by charging currents to ground in said two-wire circuit during operation of said transmitting means.

4. A telegraph signaling system including a polar relay having a line winding and a secondary winding, and signal transmitting means for sending signal impulses through both of said wind-v ings, and a two-wire line circuit including a remote receiving equipment, both wires of said line circuit being connected to a point between said transmitting means and said line winding.

5. A telegraph signaling system in accordance with claim 2 in which said line circuit is serially connected between said transmitting means and said line winding.

6. A long two-wire line circuit, signal transmitting means including a source of signaling potential at one end of said line circuit, receiving equipment at the other end of said line circuit, a polar relay at said one end of the line circuit having one winding connected over the two wires in series of said line circuit to said transmitting means and having another winding connected through a local circuit to said transmitting means.

'7. A telegraph signal repeater operating into an outgoing line circuit and comprising a transmitting relay having contacts, a receiving relay having a line winding and a second winding, a balancing circuit connected through said second winding to said contacts, said contacts being connected to the line side of the outgoing line circuit,

l and said line winding being connected to the return side of. the outgoing line circuit.

8. In a differential telegraph repeater, transmitting contacts connected to the line side of an outgoing circuit, a receiving polar relay having a line winding connected to the return side of said outgoing circuit, and a second winding connected in a balancing circuit from said contacts, circuit means connected to one of said windings to substantially equalize the phase relation of impulses in said windings transmitted by said contacts.

9. A differential telegraph repeater in accordance with claim 8 having a sole regulating means for adjusting said repeater for different operating conditions consisting of an adjustable impedance connected to said line side.

l0. A differential telegraph repeater system comprising a polar receiving relay having a line winding and a second winding, signal transmitting means, a balancing circuit connected through said second winding to said transmitting means, a phase controlling network connected between said line winding and said transmitting means,

and a two-wire outgoing line circuit connected across said network.

1l. A repeater in accordance with claim 7 further comprising a phase correcting capacitance connected in a local circuit between said contacts and said line winding, and a variable resistance connected between said contacts and said line side for adjustment of the line current.

l2. A long two-wire line circuit having capacity to ground, transmitting means connected to the line side at one end of said two-wire circuit, receiving relay means having a winding connected in the return side at said one end of. said twowire circuit, a balancing circuit to prevent said relay from responding to the operation, of said transmitting means including current regulating and phase correcting means connected to said line winding and a balancing winding on said relay connected to said transmitting means.

13. The combination in accordance with claim 6 further comprising capacitance circuit means in series with said one winding and connected in multiple to said line circuit and inductive circuit meansV in series with said other winding.

WALTER W. CRAMER.

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