US1629552A - Program-selecting circuits - Google Patents

Description

Why 24, 1927. 1,629,552

M. ECSTRIEBY PROGRAM SELECTING CIRCUITS Filed D80. 10. .1923

A lnoudlre [Iii- 51:

Jfriez I W J ATTORNEY F. 3 y INVENTOR Patented May 24, 1927.

UNITED STATES PATENT OFFICE.

MAURICE E. STRIEBY, 0F MILLBURN, NEW JERSEY, ASSIGNOR '10 AMERICAN TEl'iE PHONE AND TELEGRAPH'GOMPANY, .A. CORPORATION OF NEW YORK.

PROGRAM-SELECTING cmcurrs.

Application filed December 10, 1923. Serial No.6?9, 721.

This invention relates to transmission systems for transmitting programs over wires, and more particularly to arrangements for the selection of programs for such systems.

lVhere wire lines, such as ordinary telephone lines, for example, are used for the transmission of programs, such as news, leotures, concerts, and the like. it is desirable that some arrangement be provided whereby the subscriber, may auton'iatically select the particular program which he desires to hear. In accordance with the presentinvention, it isproposed to accomplish this result by providing a selective switch at the central oflice which may be clirectively controlled by the subscriber to connect the. terminals of the subscribers line to the terminals of any one of a. number of trunks each leading to a dif-' ferent program. i By the use of a directively controlled selective. switch for selecting a program, it becomes immaterial whether the program be transmitted at "oice frequencies or carrier frequencies, and it also becomes immaterial -whether the several programs be transmitted at thesame frequency or whether different carrier frequencies are used for differentprograms The directive switch may becontrolled by impulses or groups of impulses of alternating current and the source of current for operating the switches may be located either at the central'station or at the subscribers station Preferabl the switches are operated in accordance with the present invention over the sides of the line in series.

The inven'tion'will now be more fully understood when read in connection with the accompanying drawing, Figure l of which illustrates .how a directii e switch operated by alternating. current may be used to-select programs transmitted at ordinary telephonic t're uencies; Fig. 2 of which shows how a simi ar switch may be used to select carrier Frequency programs, and Fig. 3 of which shows a. circuit arrangement similar tothat of Fig. 2 but so arranged thatthe alternatingcurrent source for operating the switches willbe located at the central station. i v

Referring to'Fig; 1,- L designates, an ordinary telephone transmission line terminating in the; usual subscribers set S at, one end andterminating at the central oflice in the SM, a switchin usual switching jackJ. Normally the tele phone line L is connected over the contacts of a cutoff relay GO to the windings of the line relay LR. The line relay, as is usual, may comprise two windings, each of about 1000 ohms. The upper winding is associated with the tip side of the'line and is inductive. The lower winding is associated with the ring side'of the line but is non-inductive and consequently, does not-m netize the core 01' the relay when current ows through said winding. The cut-01f relay CO is so arranged that when it is operated the line relay LR is disconnected from the line; L and the line is connected directly to the tip and ring terminals of thejack J.

In order that the line may be used for program transmission purposes'dnrin such time as it is not being used for or inar telephone purposes, a program receiver such asthe loud speaker-LS 1s provided at-the subscriber statiom'said receivingdevice being bridged across the line through the back contact of the switchhoo'k 10. hen the substation set S is used for ordinary telephonic purposes, the removal of the receiver from the switchho'ok opens the circuit of the loud speaker LS so that it may not be thenused for receiving programs. At the central ofiicesa. pair of conductors 11 are con nected. from the back contacts of the cutoff relay O0 to the wipers 12 of a directive switch DR. The switch DR may he stepped by means of the stepping magnetSM into connection with any one of a number of trunks A, B, C or D, leading to difierent voice frequency programs.

In order to operate the stepping ma net I device such as a dia or key K is provided at the subscribers station for sending impulses of alternating current-over the line to energize the 'marginal stepping relaySR. The source of a1- 'ternating current at the subscribers station is bridged across the line over the back contact ot the switchhook 10. The alt-ernat- 'ing curreutior operating the switches may be obtained from the power mains at the subscribers premises. The alternating cur- '1'-ent relay'SR is connected across the back contacts of the cut-off relay CO in parallel with the windings of the line relay LR.-

The operation is as follows: When the line L isnot in use for telephone purposes and the subscriber desires to hear a program, such as C, for example, the subscril-ier Wlll merely actuate the dial or key K to send impu ses from the source G through the :tuned bridge (xmtrolled by the key K. These impulsesspuss from one terminal of the transformer 13, over the key K, buck contactvof the switchhook-IO, over the ring side of the line L, lower back Contact of the cut-off relay GO, through the tuned circuit of the. alternating current relay SR, Over the upper back contact of the cut-off relay-CO, over the tip side of the line L to the opposite terminal of the transformer .13. The ringer at. the subscribers station is ordinarily tuned to vrespond to n fre- 'queucy of about '20 cycles per second, and since the frequency of the alternating current supplied 'to the ower mains at the subscribers' stat-ionnwil. usually be in the neighborhood v0.1? (50 cycles, it will hc .apparout that the current impressed upon the line by the 'key'K will not '-.operu.te the'subscribers bell. The line relay LR is not responsive to lternatingcurrent; The current flowing through the relay SR energizes snid relay so 'that thefimpulses sentby the key K areftrnnsmitted by the relayv SR to the stepping magnet SM, Accordingly, the dl.

i l-ECtlVQ [switch DR is operuted step by step 'by the mechanismconventionally indicated to adviz'nce the wipers 12totheter1nina1s of [th trunk leading to the program C, The currents for this program are now transmitted overthe wip'erslil and conductors 11,

7 .over the back contacts of the cut-oil relay ,CO and over the line L to the loudspeaker -IlSr i If, while the circuit is being; used for .pro'- gram purposes, the subscriber desires to make {1itelephone ,call,,he merely removes the receiver from. the jsw-itchhook in the usual manner, The 10nd speaker-LS is disconnected-acute back Contact of the im}:-

. t t e lished through the substation set from bat- =tery ,'through the upper winding of tho-line relhyg-LB, over thevbnckfcontnct of the cut,

off relay CQ, over the tip "side-of the line .1), over the switchhook l0,.bi1;.ck over,the

ring side ofthe line L, back contact of the cnt-ofi' relay CO and through the noninductive winding of the relayL'R .to ground. The line relay LR is et once energlzedand upon attracting its armature, causes the hue lam (not shown). to;glow in the man man ner. The-operator, upon noticing this sigmil, will insert the plugofthe cord circnlt into the jack J, thereby'nctneting the 'cut- ;ofi' :relay' CO; The cutoff, relay connects the line Let its front contacts .to the tap and ring "terminals of the jack .l and at the same time disconnects the line L fro nfthe line relay LR, the steppin ,,,,relay sue-d the progranr connections 11 lead ng to the switch DH. The call is then completed in the usual manner. At the end of the conversation the subscriber hangs up his receiver and the operator withdraws the plug from the jack J, releasing the cut-off relay CO. This at once connects the line L to the progren'a connections 11 and the subscriber may continue to hear the program being transmitted.

If. while the. program is being received, a telephone call should come in for line L, the operator will. insert. the plug of her cord into the jack J, thereby operating the cut-ofl' relay as before. The line L will now be disconnected from the program connections and will be connected over the front contacts of the cut-off relay to the terminals of the jack J. In 'onswer' to the ringing signal, the subscriberwill remove his receiver i-rom the switchhook and disconnect the loud speaker LS. It will be observed that it the line is beingused for telephonic purposes it is impossible to set the directive switch DR, for the key K is disconnected as soon'ns the subscriber removes 'his receiver from the switchhook and the selecting relay SR at the central station is disconnected as soon as the cut-ofi' relay CO is operated.

The same arrangements may be used for selecting any one of u number of carrier programs as illustrated in Fig. 2. In this case. where the programs are transmitted at carrier frequenciesit is to be observed thntthe line may be used simultaneously for receiving program transmission und'for ordinary telephonic. purposes. Consequently, the connections ,11 extending to the wipers 12 of the directive switch nre extended .to

the tip and ring sides of the line L adjacent lzothe armature connections of the cut-off relay, so that the operation of the cut oif relay will not disconnect the rogram connectionsll from the line L, t e cut-off relay in this instance merely serving to disconnect the line relay LR and the stepping relay SR.

' At the subscribers station the loud spealc er LS is bridged across the line independently oi? the switchhook 10, so that the re- .niovnl ofzth'e mceiver from the switclihooli .cloes not disconnect the loud speaker.

by the use of the directive selective switch,

it is possible to useithe sumecnrrier frequency for all of the programs $11106 but one program will be transmitted over a line at a time. At the subscribers station it will be'necessaryto provide suitable detect ing apparatus and in most cases amplifying apparatus, as conventionally indicated at AD, in order toitranslate the carrier program into voice frequency currents for operating the loud speaker. No selecting upparatus is necessary at the subscribers station even in the case of carrier transmission, except a single high pass filter conventionally indicated at HP, this filter being provided to prevent the voice frequency currents transmitted O'\1.",tl1e line from actuating the loud speaker. The high pass filter will, of course, pass the carrier frequencies used for program transmission, regardless rent step ing relay SR. Itwill be observed that if t e subscriber removes hisreceiver from the switchhook, he will be able to hear the current from the source G, as said source is, in effect, bridged across the two sides of the line through the windings of the relay SR and over the back contacts of the cut-ofi' relay C0. As soon as the operator answers his signal, however, the cut-off relay CO is operated and in connecting the terminals of the line to the jack J, the cutoti' relay functions to disconnect the relay SR as well as the line relay LR from the line, Consequently, the tone due to the al- .ternnting current source will cease before any conversation takes place over the line. The operation of the circuit of Fig. 3 is otherwise similar to that of Fig. 2 and need not be further described.

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

What is claimed is:

1. In a program distribution system, a. subscribefis telephone line terminating in a subscrihers telephone apparatus at the subscribers station, switching means at the cen-.

trnl office whereby connect-ions may be established between said subscribers line and another subscribers line, a plurality of trunks at the cent-rel oilioe upon which programs may .be impressed, at directively operuted.

switch independentotsaid first mentioned switching means at the central oilice for-establi'shing connections between said first mentioned line and any desiredtru'nk to the exclusion of other trunks, an alternating current control device for operating said switch, and means to control the transmission of alternating current to said device from the subscribefs station over the two sides of said first mentioned line in series.

2. In a program distribution system, a

snhscrihers telephone line terminating in a subscribefis telephone apparatus at the subscribers stat-ion, switching means at the cen tral office whereby connections may be est-ablished between said subscribers line and onother subscribers line, a plura'lity ot' trunks at the central oflice upon which programs may be impressed, an impulse-operated switch independent of said first mentioned switching met-111s at the central office to select any trunk to the exclusion of the others, an alternating current responsive device for controlling the operation of said'swit'ch, and means at the subscribers station for controlling the transmission of impulsesot' alternating current "over the two sides of said first mentioned line in series to operatesaid device.

3. In a program distributionsystem, a subscribers telephone line terminatingin' a subscribers telephone apparatus at the subscribers station, switching means at the central oflice whereby connect-ions may be established between said subscribers line and another subscribers line, a plurality of trunks at. the central oflice upon which programs may be impressed, an impulse-oper ated selecting switch independent of said first mentioned switching means at the 'centrill oflice to select any trunk to the exclusion of the others, an alternating current responsive device for controlling said switch, an impulse sender at the subscribers stat-ion, and means whereby said sender may control the transmission of impulses of alternating current over the two sides of said first mentioned line in series-to operate said device.

4. In a program distribution system, an ordinary telephone subscribers line terminating in a subscribers telephone apparatus at the subscribers station, switching meansat the central oifice for establishing connec tions between said. subscribers lineand other subscribers lines so that telephone conversations may take place at ordinary telephonic "frequencies, a plurality of trunks at the cen tral ofiice upon which different programs may be impressed at carrier frequencies, a directively operated switch independent-v of said first mentioned switching means at the central 'oflice for establishing connections between said first'mentioned line and any desired trunk to the exclusion of other trunks,

controlling said switch, and means at the snb scribers station tocontrol the trnnsniis- Si0l1 of alternating current over the two sides of said first mentioned line in series to operate said device.

7 5. In a. program distribution system, 21 n ordinary telephone snhscribers line. termi- Hating inn subscl'ihers telephone :ippnrntns atthe .suhscnihefis station; switching means ant-the centre-l oflice'for establishing connections between said snbserihers line and other subscribers lines so that conversations may take plat-e at ordinary,telephonic frequencies, a plurnlit of trunks n-t'the centrnl office-upon which differentprograms may be impressed at carrier frequencies, a step-W step switch indepemlontof said first. i,-ic'nitioned switching means at the central elite-e to select any trunk .to the exclusion of the others, an nltei-nnting current responsive do Nicefor the. control. of said switch, nind means at the enlisciihers station tor-controlling the transmission of alternating; current over the ,two sides of said iii-st mentltm f-til line in series to operate saiddevice.

6. In a program distribution system, an ordinary telephone subscribers line terminating in n snbscrihere telephone z 'ipnrntns nt the snhscribefs station, switching means at the central oll ice for esthhlishing connections between said snbscrihers line and other snbrcrihei-S lines to thatconversations may take place at ordinnry telephonicfrequencies, a plurality of trunks .nt thecentral oflice upon which. different programs n'layhe impressed nt, carrier freq uencit s, an impulseopei'ntcd switch independent of said first mentioned switching means at the central oilice to select any trunk to the exclusion of the others, an alternating current respon- MAURICE 1+3. STRIEBY.

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