US2400908A - Electrical signaling system - Google Patents

Description

'M ay 28,1946. R B ss V 2,400,908

ELECTRICAL SIGNALING SYSTEM Filed July 1'7, 1942 INVENTOR ROBERT mwmonp BIRSS ATTORNEY Patented May 2 8, 1946 UNITED STATES PATENT orrlcs ELECTRICAL SIGNALING SYSTEM. Robert Raymond Birss, Harrogate, England Application July 17, 1942, Serial No. 451,305 In Great Britain September 23, 1941 2 Claims i ('01. 179- -16) I lines over which the impulses are transmitted produces a distorting effect On the wave shape of each transmitted signal impulse, which efiect is operative on the fall and rise of current at the beginning and end of each impulse, so'th'at the received impulse Wave shapes instead of having the substantially rectangular form which they possessed at the transmitting end have decremental and incremental slopes approximately a characteristic respectively of the discharge and charge of a condenser through a resistance.

The invention'has for its general object the provision of a simple and eflicient method of correcting distorted direct current impulses.

According to one feature of the invention in order that a signal responding device may respond rapidly to changes of'current corresponding to the beginning and end of a signal impulse,

the signal responsive device is subjected to a dual control, one corresponding to the current as received and the other derived from surge voltages created at'th'e beginning and end of each impulse to assist the operation or restoration respectively of the signal responsive device.

According to another feature of the invention the line signaling current is caused to flow at a receiving point through a windingof a transformer,'the voltage developed across resistance in a line or lines from a distant impulse sending or repeating point. x

The correcting device shown may form the impulse receiving part of an impulse repeater or of a selecting switch operable over a junction line in an automatic telephone'system and it is assumed in the present instance that the line come prises the single conductor l0 which on seizure by the distant transmitting point is assumed to be earthed viathe impulsing contacts I I.

The line I0 terminates on the primary winding of transformer TRI which is connected toith'e earthed exchange battery via resistance RI. 'The automatic bias resistances R3 and R4 ensure that the grid of valve V will normally be negatively biased with respect to the cathode by a potential such that the valve will pass negligible current and will neither operate nor hold the impulsing Y relay'A which is connected in circuit with the 7 its normal condition and sufficient anode current.

the circuit of said winding being efiective on the grid of a thermionic valve in the anode circuit of which is an impulse receiving relay, while the transformer is so arrangedthat surge voltages generated therein at the beginning and end of valve anode circuit having incremental and decremental slopes which are very steep.

The invention will be better understood from the following description of one method of carrying it into effect, reference being had to the accompanying drawing.

This shows circuits of a current operated impulse shaping device for correcting -the characteristics of direct current impulses received over mental slope of the fall of anode current reanode voltage supply source for the valve and is 20 preferably of the high speed type.

When the correcting equipment is taken into use by the connection of earth via impulsing contacts I I to line I0, current flows through the primary winding of transformer 'I'RI, which is preferably of low inductance, and through resistance RI to battery, whereupon the voltage developed y. across resistance RI is communicated via the secondary winding of transformer TRI and resistance R2 to the valve grid which it renders less negative with respect to its cathode than in thereupon flows to secure the operation of relay A.

During the rise of current in the primary windj'ing of the transformer at commencement of the signal a voltage is induced in the secondary wind- .ing which serves to augment the rising applied voltage derived from resistance RI and so steepens the initial rising slope of the wave form of the anode current flow. y 0n the first break impulse of a dialled impulse train, contacts II open and the current flow in the primary winding of the transformer falls, whereupon the potential on the valve grid reverts correspondingly towards its normal negative value. During the fall of signal current a voltage is again induced in the secondary winding of the transformer which voltage tends to as-. sist in restoring the normal negative potential on the valve grid and by this means the decresulting from the beginning of the break impulse is considerably steepened and relay A releases ll reclose, the current again rises in transformer TRI, whereupon the grid is rendered less negative in the same manner as for the beginning of* the signal current, and relay A re-operates. Transformer TRI functions as before to steepen the rising slope of the impulse and the resulting of output circuit connected to leads l2 and I3.

It will be appreciated that the correcting device is not limited in application to the particular arrangement shown as either 100p impulsing or single leg impulsing could be employed as desired. The voltage developed across resistance RI could moreover be arranged to cause a decrease in the normal anode current of valveV and so release a normally operated relay A in its anode circuit, which relay would be provided with a normally closed break contact instead of a make contact as shown.

In cases where the received signal is so dis-.

torted that the desired correction cannot be achieved in one stage it is possible that advantage might be gained by using a two-stage correction arrangement in which the partially corrected signal would be passed from a first stage through a second stage before being extended to the output circuit.

It will be appreciated that the invention is not limited to the construction illustrated but that modifications may be made therein without departing from the spirit of the invention. It will also be understood that the invention is applicable to alternating current impulses after rectification where there-is sufficient current output to ensure that changes thereof will appreciably affect the grid voltage, for'instance it may be used in a second stage of a voltage impulse-correcting device described in my co-pending, application Ser. No. 451,306, filed on the same day as the; present application.

I claim:

1. In a signaling system, an electronic valve having a control grid, a circuit connected to said v impulses of such polarity as to produce in said resistor a voltage tending to bias said grid positively, thereby to render said.valve conductive, the two windings of said transformer being so related that the surge voltage induced in said one winding by said second winding at the beginning of each impulse tends also to bias said grid positively thereby to increase the speed with which said valve becomes conductive, and the surge voltage induced in said one winding by said second winding at the end of each impulse tending to bias said grid negatively thereby to increase the speed with which said valve becomes non-conductive.

2. In a signaling system, an electronic valve having an anode, a cathode and a control grid, a source of direct current potential, two resistances each having one end connected to the cathode of said valve, the other end of the respective resistances being connected to opposite terminals of said direct current source, a cone nection from the positive terminal of said source to the anode of said valve, a connection from the negative terminal of. said source to the grid of said valve, whereby said va ve normally is biased to cut off, said last connection including, in series, a third resistance and one winding of a transformer, a circuit including, in series, said third resistance and a second winding of said transformer, means for impressing upon said circuit impulses of such polarity as to produce in said third resistance a voltage tending to bias said grid positively, the growth of current in said second transformer winding at the beginning of each ,7

such impulse effective to induce in said one winding thereof a surge voltage tending also to bias said grid positively, whereby said valv is rendered conductive by each said impulse, and the decay of current in said second winding at the end of each impulse efiective to induce in said one Winding a surge voltage tending to bias said grid negatively, thereby to accelerate the cut on of said valve.

ROBERT RAYMOND BIRSS.

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