US1752325A - Reduction of static interference in carrier systems - Google Patents

Description

April 1, 1930. D. E. BRA'NSON REDUCTION OF STATIC INTERFERENCE IN CARRIER SYSTEMS Filed Nov; 15

(Carrier) 1 in? 1/11/22 610 earner} line . INVENTOR BY BEBm/nswm ATTORNEY Patented Apr. 1, 1930 UNITED STATES PATENT OFFICE DAVID E. BRANSON, OF RIVER EDGE, NEW JERSEY, ASSIGNOR TO AMERICAN TELE- PHONE AND TELEGRAPH COMI'ANY, A CORPORATION OF NEW YORK REDUCTION OF STATIC INTERFERENCE IN CARRIER SYSTEMS Application filed November 15, 1928. Serial No. 319,654.

' vacum tubes by the superposition of the interfering pulse upon the normal carrier current of the channel reduces the current which operates the receiving relay so that a false spacing signal may appear during a marking impulse.

In order to overcome this difliculty it has been proposed to provide in addition to the regular receiving channels of the carrier systern, an auxiliary bucking channel in which '25 no signals are ordinarily received, due to the fact that no'carrier is transmitted corresponding to this channel. When a lightning discharge occurs the auxiliary channel picks up one of the component frequencies of the lightning discharge, which is rectified to produce a pulse corresponding to the disturbin signal pulse occurring in the normal channe s of the system. This pulse is transmitted through auxiliary windings to each of the receiving relays in such a direction as to tend to hold the armature of the receiving relay upon either its marking or spacing contact, depending upon which contact it rested against at the time the disturbing impulse occurred.

As the direction of the effect of the correcting impulse is determined merely by the character of the received signal (marking or spacing) at the time the static disturbance occurs, and is independent of Whether the static impulse tends to hold the armature against its contact or to shift it, it is evident that if the static impulse occurs just at the time the signal is changing from marking to spacing or vice versa, the impulse from the auxiliary channel may tend to prolong the marking or spacing signal by holding the armature of the receiving relay against the contact upon which it then rests. In accordance with the present invention it is proposed to utilize auxiliary channels in such a manner as to produce effects upon any given receiving relay which are opposite in direction to those produced by the static disturbance.

In order to accomplish this result, two auxiliary channels are provided, one of which is a marking channel to which a carrier current is continuously transmitted from the transmitting station, and the other of which is a spacing channel to which no carrier is supplied. The effect of a static impulse upon the marking channel will be similar to that upon each receiving channel during the receipt of marking signals. Similarly, the effect of the static impulse upon the spacing channel willbe similar to that produced upon each receiving channel during the receipt of spacing signals. By means of a reversing relay the marking channel may be connected to a suitable windingof any given receiving relay when it is receiving a marking signal and thereby produce in the relay an effect Which balances out the effectof a static impulse. When the relay is receiving a spacing signal, however, the reversing relay will shift the connection to the spacing channel, thereby producing an effect in the relay opposing that of the static disturbance. In this latter, the effect of static disturbance is neutralized or balanced out in the relay in such a manner as to enable the relayto respond to a change from marking to spacing or vice versa without any prolongation of the existing signal due to the effect of the auxiliary channel.

The invention will now be more fully understood from the followin description, when read in connection wit the accom panying drawing, the figure of which is a circuit diagram illustrating a preferred embodiment of the invention.

Referring to the figure, the various currents of the multiplex carrier system are received in a circuit RL which may be con- I drawing, and of these a description of one.

for example, channel No. 2. will sutlicc. This comprises a tuned selecting circuit T asso ciated with the circuit RL for selecting the carrier frequency f assigned to the channel. Vacuum tube amplifiers A and A are provided for amplifying the carrier frequencies. A rectifying vacuum tube D is also provided for translating the carrier frequency into di' rect current signal impulses. The grid of the Vacuum tube D is so biased by means of a C battery that with no carrier current present. no current will flow in the plate circuit. \Vhen carrier current isapplied to the grid. however. the rectified one-way current flows in the plate circuit of the rectifier tube D The operating winding V of the receiving relay RR is included in the plate circuit of the rectifier. A biasing windil'ig Y is also provided, and by means of a suitable re sistance 1' the current flowing through the biasing winding is made equal to about onehalf the current supplied from the plate of the detector D when the carrier is being re ceived.

In the system as illustrated it is assumed that carrier current is transmitted during the marking interval and that no carrier current is transmitted during the spacing interval. Normally when no signaling is taking place the carrier current is continuously on the circuit so that a steady direct current flows through the winding W to hold the armature of the receiving relay RR upon its marking contact in spite of the normal biasing current through the winding \V Each time a spacing signal is transmitted by interrupting the carrier current the rectified current through the winding ceases and the armature is shifted to its spacing contact by the pull due to the biasing winding \V The efiect of a lightning or other static interference upon the system so far described is as follows: It at the time the lightning discharge occurs a spacing signal is being transmitted so that normally no 'arrier would be present. the selecting device T ot the channel will pick up one of the com poncnt frequencies of the li; ;hting discharge which corresponds to the frequency of the channel so that this frequency will be amplitied and impressed upon the rectifier D to produce a short pulse of direct current, tending to shift the armature of the receiving relay BB from its spacing contact to its marking contact, thereby causing a false signal. It the lightning discharge should occur during the transmission of a marking signal. the effect will depend upon the magni tude of the energy of the static discharge at the frequency corresponding to the channel. If this energy is not so large as to overload the tubes of the system it merely tends to pro duce a larger rectified current in the plate circuit of the rectifier l) so thatthe ctlcct upon the winding TV; is to increase the pull tending to hold the armature upon its ma rking contact. It. however. the energy ot' the static discharge is very large. so as to overload the various tubes of the system. thereby producing crowdiug' of the normal carrier currents of the channels. the carrier current for each channel is reduced in amplitude to make room. as it were. for the excess energy of the lightning discharge. This reduction in the carrier frequency of the particular channel now under consideration may result in a decreased current in the plate circuit of the rectitier I): so that the winding \Y i no longer able to hold the armatur aga nst the pull of the biasing winding. This ('ZlllHt a false spacing signal.

In order to correct for these false signals. two additional channels are associated with the circuit llli. one of the channels being a so-called marking channel to which a carrier current is continuou ly transmitted from the transmitting station and the other of which is a so'called spacing channel and to which no carrier current is transmitted from the distant transmitting station. The marking channel consists of a selecting circuit T for selecting the frequency f assigned to this channel. The cl aunel also includes amplifiers MA and MA. similar to the amplifiers already tltrt'llllttl in connection with channel Xo. 2. The marking channel also includes a dctcctor for each receiving channel of the system. For example. the detector Billis associated with the marking channel tor receiving channel No. l and the detector hill is likewise associated with the marking channel for receiving channel No. l. 'l hese detectors are in all respects similar to the detector I) already dt ('l'lll0d and supply to their plate circuits continuous direct currents tleii-l'lllllltll by the amplitude of the received carrier.

The spacing channel dilhu-s from the marking channel in that no carrier current is transrritted thereto from the distant transmitting station and its selecting circuit T is tuned to a t'requeucy which is difl ereut from the frequency of the marking channel and also from the various carrier frequencies assigned to the signal receiving channels. The spacing channel includes amplifiers SA and SA in all respects similar to the correspondltltf lfltl If E ing amplifiers of the marking channel. Likewise, as in the case of the marking channel, detectors, such as SD and SD are provided for each of the signal receiving channels; No current flows in the plate circuits of the detectors associated with the spacing channel under normal conditions. If, however, a static impulse occurs, the channel selects a frequency component thereof corresponding to the frequency of the channel and thereby causes a rectified current pulse to flow in each of the detectors associated with the spacing channel. 7

Each receiving relay controls polar switching relays. For example, the receiving relay RR controls polar relays PR and PR for the purpose of reversing the circuit connections to the auxiliary channel, in a manner to be described later. Likewise, the receiving relay RR controls polar relays PR and PR, in a similar manner.

The operation of the marking and spacing channels may now be understood from a description of their effect upon the receiving channel No. 2. Normally, with the marking signal bein received by channel N0. 2, the armature o? the receiving relay RR will be upon its marking contact and the polar relay PR will have its armature upon its upper contact, so that the plate circuit of the detector MD (which is associated with the marking channel) will be connected to the biasin winding VV This increases the norma biasing current due to the resistance r, by an amount determined by the amplitude of the received carrier of the marking channel. In order, therefore, to maintain the normal relation between the currents flowing in the operating and biasing windings, the polar relay PP, is arranged to coir ncct to the operating winding a resistance r: in parallel with the plate circuit of the detector D the resistance 7': being so proportioned as to draw through the winding a current in addition to the plate current of the detector D said additional current having a value equal to the plate current normally supplied to the winding Y, from the detector hlD hen a'spacing signal is rc ceived due to the interruption of the carrier frequency f supplied to channel X0. 2, the receiving relay RR shifts the armature to its spacing contact. thereby causing the polar relays PR; and PR to shift their armaturcs to their lower contacts. The polar relay PR disconnects the biasing winding from the detector MD of the marking channel and connects said winding to the detector SD 'ot' the spacing channel. As no current normally flows in the plate circuit of the detector SD the armature of the polar relay PR is arranged to disconnect the resi tance 1" from the operating winding during the spacing condition so that in the .nels, the plate current of the absence of any static disturbance no current flows through the operating winding V As has already been pointed out, the effect of static upon the signalbf any given channel depends upon whether the channel is at that moment receiving a marking or a spacing signal. It a marking signal is being received in channel No. 2, for example, the polar relays PR and PR will have their contacts upon their upper armatures so that the marking channel will be connected to the biasing winding Under these conditions the current drawn through the biasing wind ing W by the plate of the detector MD of the marking channel is just balanced by the current drawn through the operating wiud ing W by the resistance I'- The current drawn through the latter winding by the plate circuit of the detector D however. is substantially twice that drawn through the winding W by the resistance 13.

NOW if the cited; of the static impulse is such as to overload the tubes in the tran nif sion circuit and cause crowding of thc thandetcctor i); will be decreased, and if it should be, decreased to such an extent that the total current through the winding is less than that through the winding the armature of the reccfrinu' relay would be shifted to its 'slmtii'lg' condition, thereby causing a false signal much as the marking cha nel i r carrier current, however, thl carrier c1 will be decreased'in volume just a the car rier current supplied to channel he. 2 dur ng themarking signal. oit eqitenti v. the plate current of the detector T\ll. (and other dete tors associated with the marking channel) will be decreased accordii'igly so that there will be a decrease in the currcnt flowing through the winding V which conipar able to the decrea e in the current flowing through the winding It the marking signal should end while the static disturbance is continuing, the interruption ot' the carrie frequency transmitt d to the receiving channel No. Q will reduce the current through th winding V: and permit the biasing sindi to shift the relay armature to its spacing contact not.rith;-tanding the static inipu e.

In case the condition or" the tifzttl ili circuit such at the static inipul; e d overload the tu es. the e'ilect upon :12. vidual channel. such as channel be to increase the plate current of the dc tor tube D and thereby li (2itt1r-t= the curzcnt flowing through the winding c V The eti'c t upon the marking channel, however, is to similarly increase the plate current ot the detector tube, such as MD so that there will be a corresponding increase in the current flowing through the winding V Should the signaling channel No. 2 change from marking to spacing while the static impulse continues, the interruption of the carrier supplied from the distant station will reduce the current flowing through the winding N: to permit the relay to shift its armature to its spacing contact. The shifting of the armature from marking to spacing during the continuance of a static impulse, resuits in shifting the armature: of the polar relr vs PR and PR thus establishing the circuit in condition to neutralize the effect of static during a spacing signal.

When any channel, such as channel No. 2, is receiving a spacing signal, the armature of the olar relay PR shifts the connection of the iasing winding from the marking channel to the spacing channel while the polar relay PR disconnects the resistance 1' from the operating winding In the absence of any static effect, no current will flow through the winding (the plate current of the tube D being substantially zero during spacing), and the current flowing through the biasing winding V will be only that drawn by the resistance 1- If a static impulse should occur While the circuit is in spacing condition, the selective circuit T of channel No. 2 would pick up a component whose frequency corresponds to that of the channel, so that a current would flow in the plate of the detector D and hence, in the winding W If this current should be larger than the current drawn by the resistance r a false marking signal would occur were it not for the connection over the armature of the polar relay PR, to the plate circuit of the detector SD of the spacing channel. Due to this connection, however, the static component picked up by the spacing channel causes a current to flow in the plate of the detector SD and through the biasing winding V to balance the static current flowing through the operating winding W Consequently, the false signal will not occur. If the static impulse should con tinue after the spacing signal received by the channel had ceased and the marking signal begun, the current flow through the operating winding W would be increased by an amount determined by the amplitude of the received carrier, thereby causing the armature of the receiving relay to be shifted to its marking contact.

It will of course be obvious that other signaling channels, such as channel No. 1, will function in a manner similar to that already described n connection with channel No. 2.

It will also be obvious that the general principles herein disclosed may be embodied in many other organizations widely different from those illustrated without departing from the spirit of,the invention as defined in the following claims.

WVhat is claimed is:

1. In a carrier system, a receiving channel comprising means to select an alternat ing Carrier current, means to detect from said carrier current a telegraph signal, and a receiving relay responsive to said signal; auxiliary channel apparatus selective of com ponents of interfering energy differing in frequency from the carrier waves to which the receiving channel'is selective; and connections from said auxiliary channel apparatus to said receiving relay and controlled by said re eiving relay to produce in said relay, in response to interference, electrical effects similar to but opposing those produced on said relay by the interference effect in said receiving channel.

In a carrier system, a receiving channel comprising means to select an alternating carrier current, means to detect from said carrier current telegraph signal impulses. and a receiving relay responsive to said impulses; said channel producing in said relay disturbing impulses in response to interfering energy superposed on the system; auxiliary channel apparatus selective of components of said interfering energy differing in frequency from the carrier waves to which said receiving channel is selective; and connect ons from said auxiliary channel apparatus to said receiving relay and controlled by said receiving relay to produce in said relay. in response to interference, impulses to neutraliZe the disturbing impulses from said receiving channel: said neutralizing impulses permitting said relay to respond to changes of the detected signal impulses.

3. In a carrier system, a receiving channel 'comprising means to select an alternating carrier current, means to detect therefrom signaling impulses, and a receiving relay having an operating winding responsive to said impulses to shift the armature in one direction and a biasing winding to shift the armature in the opposite direction: an auxiliary channel comprising means selective of interfering components differingin frequency from the receiving channel; a detecting means associated with said auxiliary channel: means to establish connections from said detecting means to one of said relay windings during the receipt of marking signals: and means to open said connections during the receipt of spacing signals.

4. In a carrier system, a receiving channel comprising means to select an alternating carrier current. means to detect therefrom signaling impulses. and a receiving relay having an operating winding responsive to said impulses to shift the armature in one direction and a biasing wind ng to shift the armature in the opposite direction; an auxiliary channel comprising means selective of interfering components differing in frequency from the receivnig channel: a detecting means associated with said auxiliary channel: means to establish connections from said detecting means to said biasing winding during the receipt of spacing signals; and

means to open said connections during the receipt of marking signals.

5. In a carrier system, a transmission circuit, a receiving channel associated therewith and comprising means to select an al ternating carrier current from said transmission circuit, mcans. to detect signaling impulses from said carrier current, and a receiving relay; an auxiliary marking channel to which a carrier frequency different from that of said receiving channel is continuously supplied over said transmission circuit; an auxiliary spacing channel for which no carrier is supplied; said spacing channel being selective of interfering components of frequency different from those of the other channels; to said receiving relay from said marking channel during the receipt of marking signals in said receiving channel, and from said spacing channel during the receipt of spacing signals in said receiving channel.

6. In a carrier system, a transmission circuit; a receiving channel associated therewith and comprising means to select an alternating carrier current from said transmission circuit; means to detect signaling impulses from said carrier current, and a receiving relay having an operating winding responsive to said impulses to shift the armature in one direction and a biasing winding to shift the armature in the opposite direction; an auxiliary marking channel to which a carrier frequency different from that of the receiving channel is continuously transmitted over said transmission circuit; said markin channel including means to select said frequency; a detector associated with said marking channel an auxiliary spacing channel for which no carrier is supplied and having selecting means to select interference components differing in frequency from the carrier frequency of said receiving channel; a detector associated with said spacing channel; and means to establish connections to one of said relay' windings from the detector associated with one auxiliary channel during the receipt of marking signals, and from the detector associated with the other auxiliary channel during the receipt of spacing signals.

7. In a carrier system, a transmission circuit; a receiving channel associated therewith and comprising means to select an alternating carrier current from said transmission circuit, means to detect signaling impulses from said carrier current, and a receiving relay having an operating winding responsive to said impulses to shift the armature in one direction and a biasing winding to shift the armature in the opposite direction; an auxiliary marking channel to which a carrier frequency different from that of the receiving channel is continuously transmitted over said transmission circuit; said and means to establish connections,

marking channel including means to select said fre uency; a detector associated with said mar in'g channel; an auxiliary spacing channel for which no carrier is supplied and having selecting means to select interference components differing in frequency from the carrier frequency of said receiving channel; a detector associated with said spacing channel; and means to establish con; .ections to said biasing Winding from the detector associated with said marking channel during the receipt of marking signals, and from the detector associated with said spacing channel during the receipt of spacing signals.

In testimony whereof, I have signed my name to this specification this 14th day of November, 1928.

DAVID E. BRANSON.

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