US1685835A - Program-selecting arrangement - Google Patents

Description

. H. M. BASQOM ET AL PROGRAM SELECTING ARRANGEMENT* @dh E, WZ. l

H. M. @Ascom ET AL,

PROGRAM S ELECTING ARRANGEMEN T Filed Dec. 22, 1925 2 Sheets-Sheet 2 INVENTUM? i Patented ldlrt.. @9 lhhii lill HENRY lill.. EASM, Ulli' Bltllhli'll, OSCAR lll.

` all will Aldilllllil), Ul lLlEUlllli., MJD MBERT L lmltGrlEtMll-SJELECTKNG RANGEMENT.

.application tiled .'hecember llt, i925. Serial lilo. TMW.

with news,` music, entertainment and the lilrey over wires. it is desirable that more than one program be available to the subscriber at a given time, and consequently7 somemethod lll of selection under the control ofthe subscriber becomes necessary. llt has been pro posed that the subscriber be provided with a dial to operate step-by-step switches to select the program in a manner analogous to that employed in machine switching methods of connecting telephone subscribers.

Yllhe problem of dialing a program. however'.I cannot be solved by the direct application of machine switching methods, since certain special problems are involved due to the fact that when the switching operation is edected, 'a plurality of subscrbers lines are connected in multiple to the same trunk, and also due to the fact that the receiving equipment used lill by the subscriber for program purposes is aloud speaker which would be very sensitiveto ordinary dialing operations.

llt is one of the purposes of the inventionn therefore, to devise a system of dialing of such character that a minimum amount of interference between lines will occur' during the operation of dialingdue to the fact that a plurality of lines are connected to each switching point.. i

Another ob'ect of the invention., is to provide a dialing system which will produce a till minimum amount of interference in the subscribers loud speaker.

Another object of the invention is to provide a dialing system which will give an indication of the number of subscribers listoning to any given program at any given time.

'llhese and other objects of the invention may be attained by means of the arrangements set forth in detail in the following description and illustrated in the accompany ying drawing.. the gures of which illustrate two circuit arrangements embodying the principles of the invention.

lleferring to Figure l7 lh designates a subscribers loop of a program distributing system. said ysubsmri u"s loop extending from ansubscribers on to a central office Y. lit the subscribers station the line terminates m program receiving apparatus comprising a vacuum tube amplifier l hav- `ing a suitable potentiometer l? interposed between its output circuit and aloud speaker (not shown). 'lhey current supply forv the amplifying tube l may be provided from an ordinary alternating current house system through va transformer Q0, a rectifying tube lt being provided for rectifying the alternating current. Ylhe filament of the amplifier l is energized by unrectified alternating current through windings 21 and 22 of the transformer 20, these windings being balanced with their terminals connected to the filament terminals and with their .midpoint connected to the plate of the tube. 'lhe filament of the rectifier lt islenergized through the secondary winding Q3, while the rectilied current for the plate circuit of the arnplifier il is supplied through the secondary winding 94C of the transformen said winding being connected in series with the rectilier R. liv means of suitable resistances 25 and 26, the proper voperating potential may be ap plied to the grid of the tube.

llt the central ollice'l', the line passes through the main distributing frame MDF and through the suitable test jacks il and d" to a transformer 30. through which the program may be applied to the line. 'lhe primary circuit of the transformer 30 may be switched into communication with any one of several programs supplied over trunks- T., 'lily ,'llg. etc., through step-by-step switching devices indicated generally at 'llhese switching devices may be operated by means of a suitable dial lll at the subscribers station said dial being connected over a simplexl circuit of the line la to operate a suitable line relay hilt., through which the impulses for actuating the stepping magnet Sill may be relayed.

llhe program trunlrs plm. T2, etc... are connected to the switching terminals of the switches. such as through cut-oft' aclrs d1, @ly etc.. whereby anv group of subscribers may be disconnected from a given trunlr as group whenever such disconnection. becomes desirable. 'llhe monitoring aclrs such as 12h de@ etc. are associated with the trunlrs to enable the operator to monitor the program i tlnoiigh a suitable monitoring eouipment lll.

Fllhe "aclrs il and df are arovided in order till tid

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that the operator may use selector test equipment and line test equipment schematically indicated at N and O, respectively. A popularity indicator P is provided for determn ing` the number of subscribers listening to a program at a given time. This device will be described more in detail later,

.The selective switching apparatus S coinprises in effect two switching u nits s, and 82, each having three rows of contacts arranged in the form of a semi-circle, so that wipers may be operated step-by-step by the stepping magnet SM to engage the various contacts successively.V Each row of contacts involves 'two complete groups of contacts, each group comprising a normal contact and a set ot' ten switching contacts individually connected in multiple with the corresponding contacts of the other group so that when the wiper of the switchA is advanced to any particular switching contact of the first group, it is restored to normal by being advanced to the normal contact in the second group. Tt thed wiper is then advanced to another switching contact, it is restored to normal by being advanced to the end of the next quadrant, whereupon a second wiper comes into play and rests on the normal contact ot the first quadrant. In this Way, the restoring operation alwaystakes place by a forward motion of the same character as the selecting operation.

The two selector bank units s, and s, are arranged to be operated from the saine stepping magnet, and the various trunks are so wired to the contacts of the corresponding rows ot the two switching unitss1 and 82 that the even-numbered trunks will be connected to the even-numbered contacts of say the switching unit s1, andthe odd-niiiiibered trunks will be wired to the odd-niimbeicd contacts ot the other switching unit The intermediate unwired contacts ot each switch will be clipped short so that the wiper, in being stepped around, does not make contact with them. and preferably they will be wired togetherl and grounded. This construction will reduce the interference during the switching operation due to leakage between adjacent contacts.- That. is to say, considering a given selector bank. as the. .wiper passes trom a contact wired to a given trunk to the next adjacent contact, that contact will be dead and .will not be connected to another trunk., Consequently, leakage currents cannot pass from a program trunk connected to the second contact across to the first contact ot the trunk and thence to lines switched to the program trunk connected to the first contact, owing to the fact that there is no program trunk connected to the second contact. This method ot wiring the switches. while it involves the use of two selector banks as compared with one, has the edect ot doubling the distance between lessees adjacent line contacts, while at the same time permitting the use ot standard switches operated by standard step-hy-step magnets taking the usual and necessary short steps.

Further details ot the invention will be clear from a descriptioirot` the operation, which is as follows:`

Assuming that the switching mechanism has' been previously advanced to select some previous program trunk, and that it is dcsired to select a difterent program. the subscriber first manipulateshthe dial D to dial Of As the dial is moved off normal, the ofi"- normal contact 40 is closed. so that ground is connected to the midpoint ot the bridge 4l. and the circuit is completed over the two sides of the line in parallelto the midpoint of the secondary winding of transformer 30, and thence to the winding of the line relay LR to battery. Line relay LR, upon being energized, completes a. wcircuit over its front contact for slow release relay SR. Relay SR.'in turn, at its outer left-hand front contact, completes a circuit for the cut-Oft relay C() which operates to disconnect the input side ot the transformer 30 troni the switching` apparatus during the switching operation. This prevents the dialing inipulses from being transmitted over the various switching contacts to other subscribers lines already listening to the programs wired to those contacts. As soon as the dial is released, it returns and sends-interrupted impulses to the line relay LR. The slow release relay SR holds up during these interruptions, and each time the line relay 'falls ott, a circuit is completed over its back coutact and the right-hand front contact of' the slow release relay SR to the stepping inagnet SM. The stepping magnet then procecds to step the wipers at the switch banks in a counter-clockwisc direction until the wipers rest upon the next '/.ero contact of each bank. This will in general require lessI than all ot the ten pulses ot the '/.ero group. lVhen this point is reached. ground is connected over the zero contact ot row .v6 and over the inner left-hand front contact ol' slow release relay SR to the windingot the stepping magnet SM. This holds the stepping magnet SM locked up during the transmission of the remaining pulses ot the '/.ero group of ten. At the end ol' the last pulse, the slow releasev relay SR releases and disconnects tlie ground troni the stepping magnet, which, upon being released. advances the switch to the next contact, which is the normal or N contact.

The subscriber now dials the digit. of the. program desired. Again, as .soon as the dial is moved oft normal, the line relay lill is energized to pull up the slow release relay SR and again operate the entoil' relayv (it). Upon releasing the dial, the pulsesy are again transmitted, and the line relay llt operates lill) neaaaaa the stepping magnet SM to advance the wipers to the particular contact desired. rlhis will not result in connecting' ground over row a; ot the bank, since the wiper. is being advanced at this time trom its normal positionj and .hence would not be advanced as tar as the zero contact.

llt will be observed that during; the dialingoperation the impulses are transmitted over a simplex circuit. y rlhe subscribers set may be connected to the line during this operation without causing the impulses to produce loud and annoying clicks in the loud speaker. ltlso, the cut-ott .relay .is operated. during each dialing operation to prevent the `impulses trom beingl transmitted to other l lines connected to the program trunk which is wired to the contacts upon which the wipers ot the operated switching` mechanism l rest at that instant. rllhe wiring ot the trunks to alternate contacts ot the switch banks. as already described, will reduce and practically eliminate interterence due to leakane between adjacent contact-s at the time a 5 switch is being advanced trom one switchi'np; point to the next switching point.

jat any time the operator may monitor the program transmitted over a given trunk by plugging` the monitor equipment lili into one o-t the jacks J1', J2", etc. 'l he operator may also test ,the selector switches by plugging` the selector test equipment M into'the jack such as d. type well known in the art and need not be described in detail. Similarly, 'the operator may make line test measurements by plug-l` ging the line test equipment yinto the jack il. These line test measurements and the apparatus used tor making the tests are well known inthe -art and need not be described in detail here.

ltany given time, an attendant may desire to know approximately how many sub scribcrs are listening to a given'program. ltor this purpose` the s: rows of the switch banks ot the various subscribersswitching equipments at the central otlice are wired in multiple to a set ot conductors l, 2. etc., leading to corresponding contacts ot a handoperated switch or dial 50. Each wiper correspondingy to the S5 row ot the switch bank is connected through a resistance '5l to ground` and the wiper ot the hand-operated switch 5() is connected through a suitable` l s milliammeter P to battery. [ttanyf given instant, the resistances corresponding to` 5l ot all subscribers switches which are connected-to a given trunk, will be connected to g the conductor l, 2 or 3, as the case may be,

lo i correspondingr to that trunk. rlhe attendant,

by moving the switch 50 to the contact corresponding to the trunk, will, by observingn the reading otn the milliammeter. be able to determine approximately how many suboa, scribers areconnected to the trunk inques- 'lFhiav test equipment is ot ation, since the current tlowingl through the milliammeter will depend upon the number ot resistances such as 5l connected in parallel to the conductor l, 2 or 3, as the case may be.

The arrangement above described involves the restoring;l ot the switching;f mechanism trom a previous selection by dialing" an tra digit. which in the case-assumed was Zero.

ingr circuit is illustrated in lFig. Q. and in this `form of the circuit the restoring,A ot the switches is controlled by a special locking key lt, so that the additional dialing operation is not necessary. ln ltig. Q, the details oit the subscribers equipment other than the dial and its connections to the line are not illustrated andare supposed to be the saine as those illustrated in Fig. l. lllikewise the network trom the trunks to the switching` equipment is omitted and the extra rows ol switch contacts s2 and s4 are likewise not shown. in order to simplify the drawing. llere. also, it is assumed that the extra -rows ot contacts and the wiring; tothe trunks will be the same as in Fig. l, and that the various jacks and testing;` equipment will beprovi ded as in lig. l.

lFurther details ot the circuit will be clear trom a description oit the operation, which is as follows:

Assuming that the switch has been previously advanced to' select a particular program, and that the subscriber desires to select a new program, the lockingI key llt is tirst actuated, thus connecting ground to the 'simplex circuit over the line L to energize the line relay llltt. rthe ground connection ot the simplex circuit is maintained as longf as the locking key llt remains locked up. ills A slightly modified arrangement ot' the dial- 'ttt' hlt leu

soon as the line relay'lllltt is energized, it y connects ground over its trout contact to energize vthe cut-ott relay Utl, thereby disconnecting the primary winding ot the transt'ormer 30 `from the switching terminals to prevent interference with other lines.- The` cut-ott' relay @U in this case is made slow toI release so that its armature does not tall ott' during dialing impulses. The line relay lult also connects ground over the lett-hand back contact ot the slow release relay Slt to the lll) wiper ot the row s3 ot the switch ba'nk andv through the various ott normal contacts ot said switch, over the back contact ot the stepping magnet SM land through the wind` ing` ot said magnet to battery. rllhis causes the selector magnet to buzz and step the selector switch around tothe normal terminal hl. Upon reachingt this terminal. the back contact ot the stepping magnet SM is opened and a circuit is completed trom ground over the front contact oit the line relay ldd-,over the lett-hand back contact ot the slow release relay Slt, normal contact ot the s3 are ot the switch bank and through the winding "proceedto dial the desired program.

`the following claims.'

of the slow release relay SR to battery. This energizes theA slow release relay which is at once locked up over its lett-hand front contact to ground atA the line relay LR independently of the wiper of the third are of the switch bank. A tone is now applied to the subscribers line over the outer right-hand front contact of the slow release relay SR and the lower front contact of the cut-ofi' relay. The subscriber, upon hearing this tone in his receiving set, knows that the circuit is restored to normal and t-hat he may i ccordingly, he mores the dial oft' normal and upon lreleasing ity-the'ground circuit through 4the line relay LR, as previously described, is interrupted, thereby 'transmitting pulses from ground over the back contact of the line relay and the inner right-hand front Contact of the slowT release' relay to the steppingmagnet. The slow release relay SR and the kcut-off relay hold upduring the transmission of the interrupted pulses. The pulses cause the stepping magnet to advance the wipers of the switch, which were previously resting on their normal contacts, to the contact corresponding to the desired trunk.A The subscriber then releases the locking key K in a well-known manner, thereby opening the circuit for the line rela-y LR. This, lin turn, restores the slow release relay SR to normal and also deenergizes the cut-off relay CO so that the subscribers line is cut throughto the desired trunk. The cut-oil relay, it will be noted, was .operated during the entire switching operation to prevent interference witlrother lines. y

lIt will be obvious that the general principles herein disclosed may be embodied in many other organizations widely different from those illustrated. without departing from thespirit of the'invention as" defined in 'i What :is claimed is: l n

l. In a program selecting system, a'subscribers line, a plurality of program trunks, switching arrangements for interconnecting the subseribers line With any desired trunk, means to control the voperation of said switching apparatus, a subscribers program receiving equipment associated with the line, a circuit extending from the subseribers Lef-asses station over the line to `said switch cont-rolling means, means controllable at will by the subscriber over said circuit for restoring the, switching apparatus to normal prior to the switching operation, and. means controlled Vby the subscriber over said circuit tor thererows ot contacts and another set. of alternate trunks are, connected to thcl even-munhered contacts ot' the other set ot rows ot contacts.

3. In a program selecting arrangement, a sulfscribes line, a plurality ot trunks leading to program stations, means to interconnect said subscribers line with any desired trunk comprising a selector switch, said selector switch involving rows of contacts forming two sets, and connections whereby alternate `trunks-are connected to the voddnumbered contacts of one set of rows ot contacts, and another set f alternate trunks are connected to the even-numbered contacts of the other set of rows of contacts, the alternatecontacts ot each set which are not, wired to any trunk being so arranged that the wipers of the switclrcannot make contact therewith.

t. In a program selecting,r system, a subscribers line, a plurality of trunks leading to program stations, a selector switch for connecting the line to a desired program,

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