US1834279A - Telegraph circuits - Google Patents

Description

Dec.1.1931. I F. w JABvls 1, 7

TELEGRAPH CIRCUITS Filed Oct. 20, 1930 l NV E NTO R. FREDERICK W.JARV|S Patented Dec. 1, 1931 umrsu ST TES Parent OFFICE;

FREDERICK wiLLIAM JARVIS, or CROYDQN, sUnnnY, NGLAND, Assieno'n T0 03min i .AND COMPANY, LIMITED, or GROYDON, SURREY, ENGLAND 1 V TZEIAQEGRAVPH ornot'rrrs I Application filed camber 2o,-193o, Seria1,No.;48 ,9 97, and'in Great. Britain-March 2c, 1930;. f

This invention: relates to telegraph systems I in which an intermediate'repeating station is connected between two terminal stations.

Telegraph systems in which signals are transmitted over a line only in one direction at any one time, are known as simplex telegraph systems. Telegraph systems in which signalsimay be transmitted simultaneously in opposite directions over a single line without mutual interference are known telegraph systems. I

In simplex telegraph systems in which an intermediate repeating. station .:is connected between two terminal stations it is necessary or desirable to arrange that either of the two receives. This necessitates switching operations at the intermediate repeating station at each change in the direction of transmission. In a double current system inwhich signal-v ling is effected by currents of opposing polarity. which is the system in most general use, this is effected by automatic send-receive switches, hereinafter referred to as autoswitches, at the repeating station which are controlled by relays, hereinafter referred to as auto relaysinserted in the line circuits in series with retransmitting relays, hereinafter referred to as transmitting relays.

In this case when one terminal station commences to transmit, the signalling current operates the auto relay to one side and the other in response to signalling current from a neutral position. At each extreme position a contact is made which closes the circuit of the auto switch which effects the appropriate switching operation for that direction of transmission. The auto switches are slow to release, are thereby maintained operated during the transit periods of the tongue of the auto relay.

According to the presentinvention, in a double current telegraph system in which switch means are required to be actuated to an operated position by signalling currents received over a line, means is provided to rectify the signalling currents in order to actuate the said switch means by unidirectional current.

The main advantage of this arrangement is as duplexthattheton'gue of the auto relay closes the I dur ng'slgnalhng, It lSJlSllfll tovmsert a shunted capacity at the receiving end of te1e graph .lines to improve the speed of working by minimizing theflefiect of self induction ofthe receiving'app'aratus. In the present invention, the effect of this shunted capaciity in series with the rectifier andthe transmitting relay is to increase the unidirectional holding current in the auto relay during signalling reversals to an extent dependent on' the relative values of the capacity and re sistance and the electrical characteristics of the remainder of the line circuit, -.-The dis tinguishing feature of the invention is that thecontact on; the ,auto relayis now firmly maintained at high signalling speeds,-where-' as previouslythe duration of contact of the tongue with the limiting contactstops was considerably reducedby the: transittime and contact bounce periodwhich increases with the speed of signalling. Further and conse quent. advantages will be apparent such. as

that due tothe reduced tendency to burning.

of the contacts and wearof the pivots of the relay;

The currentrectifier maybe of any convenient form but is preferably of the bridge type in which dry metal oxide rectifier elements are inserted in the armsof the bridge. The accompanying figure shows diagram inatically the connections at an intermediate repeating station in a simplex telegraph circuit according to the present invention.

A line 1 from a terminal station (not shown) isconnected to the armature of an auto switch 2, the normal or back contact of which is. connected through the winding of a. transmittingrelay 3, a shunted capacity 4,

and a bridge rectifier 5 to earth. The contacts of transmitting relay 3 are connected to a split battery of, whichthe junctionis earthed, and the tongue to the operated contactof auto switch 6, forthe other section 7foftheline. A relay 8 is inserted in the bridge of the rectifier 5 and whenop} erated closes the circuit through the winding of auto switch 6, which operates on the current from battery 9. The connections for the other section 7 of the line to the second terminal station (not shown) are similar to those for the first section. Line 7 is normally earthed through the winding of transmitting relay 10, shunted capacity 11 and rectifier 12. Relay 13 in the bridge circuit of rectifier 12 controls auto switch 2 for section 1 of the line, and the tongue of transmitting relay 10' is connected to the operated contact of the auto switch 2 of this section of the line.

Normally both the terminal stations would leave their terminal switches (not shown) to receive; This in efiect earths the two. sections of the line through the respective re-' ceiving means. Under these circumstances there is no current in either section 1 or7 of the line and both auto switches 2 and 6 are ina'norinal or unoperated position so thateach section of the line is connected to earth at the repeating station through the respective transmitting relays 3 and 10, shunted ca-- pacit-ies 4c and 11, and rectifiers 5 and 12;

lV-hen a terminal station, for example the terminal station connected to section 1, deslres totransmit, the switch at that terminal station is turned to send and a spacing current is, therefore, put on the line.

At the repeat ing station relay 8 thereupon operates and closes the circuit of auto switch 6 which operates and connects the tongue of transmitting relay 3' tothe second section 7 to. the line. The transmitting relay 3 responds to signal"- ling currents over section 1 oi theline-and therelayed signals are retransmitted over the second section 7 to the second terminal eta-- tion. During signalling, as previously explained, the reversals of signalling currents are-rectified by rectifier 5 and maintains relay 8 in anoperated position, due to the efite'ct of the shunted capacity 4 in series in the line circuit, the holding current through the relay 8 is even increased during periods of signalling compared with the steady spacing current during pauses.

' It will be seen that this method of control.- ling of the auto switch by auto relays which are operated by rectified signalling currents provides switching means of a very robustnature compared with the methods previously known.

It will be understood that the actual connections at a simplex repeating station need not be precisely as shown in the accompany-- ing drawing. The general arrangements are well known. The invention which it is de-- siredto protect resides in the manner of control of the auto switches and is defined in the following claims.

'l/Vhat is claimed is:

1'. In a double current telegraph system, a, line circuit, switch means actuated to an operated position by signalling currents received over said line, means to rectify said signalling currents to actuate said switch means by unidirectional current and hold said switching means actuated during reception of signals, and a retransmitting relay responsive to signals received over the line circuit to repeat signals into a line controlled by the actuated switching means.

2. In a double current telegraph system,

intermediate repeating apparatus connecting two sectionsoi a line, switclrmeans therein to. control the direction of retransmission current, rectifying means inserted in each section ofsaid line to convert.signalling currents into unidirectional current, and means responsive to said unidirectionalv currentto control; said switch means.

In double current simplex telegraph repeating apparatus, a bridge rectifier, a shunted capacity and a winding of a signal retransmitting relay together connected? in series: in each of two'secti'ons of a line, an auto relay connected in the bridge circuit of said rectifier and actuated to an operated position by signalling currents rectified thereby, and. an auto send receive switch controlled by each of said auto relays.

4.. In double current: simplex telegraph repeating apparatus-a metal oxide bridge rectifier: connected in a line circuit, an auto relay connected in the bridge circuit of said rectiher and; operable by line currents rectified thereby, and an. auto send-receive switch controlled. by said auto relay- In witness whereof I hereunto subscribe my namethisfourthday of September, 1930.

FREDERICK \VILLLAM J ARVIS-

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