US2476888A - Toll line remote group busy signaling - Google Patents

Description

July'l9, 1949. G. w. MITCHELL TOLL LINE REMOTE GROUP BUSY SIGNALING Filed Feb. l19, 1948 v:2 sheetssheet 1 INVENTOR.

GEORGE Vl MITCHELL Zziga ATTORN E Y July 19, 1949. G. w. MITCHELL. I I 2,476,888

TOLL LINE REMOTE GROUP Busy SIGNALING Filed Feb. 19, 1948 2 sheets-sheet 2 I I EXCHANGE A ExcHANGEB A. C. SOURCE EouI SIG' ExcILc LINE EouIR 5.

` LINES To sos. CHAIN I INE ExcILB- '21000 RLY. EQUIP. 64 TER I I 15 'r6 4 49 L 47 EXCHANGE c EP l 82 ausv sla a cHAIN m SERIES THRU CHAIN RLXSOF OTHER LINE EQUIP EicHANeE o INE EouII. NAIN RLY SCEG- sERIEs Trnu cHAIN LEsIboF OTHER LINE 91 LINE EOUI 1N V EN TOR. GEORGE W. MITCI-ELL FIG.2 I

ATTORNEY EQ UIP.

N RLY ExcH. u l

BUSY SIG.

Patented July 19, 1949 TOLL LINE REMOTE GROUP BUSY SIGNALING George W. Mitchell, Ann Arbor, Mich., assigner to Automatic Electric Laboratories, Inc.,v Chlcago, Ill., a corporation of Delaware Application February 19, 1948, Serial No. 9,413

Claims. 1

The present invention relates in general to supervisory circuit arrangements whereby group busy indication is given at distant exchanges whenever a group of line (toll) circuits outgoing from a center, or tandem, exchange to another distant exchange become busy.

In a network of exchanges including a number of terminating exchanges and a tandem exchange common to the terminating exchanges, an operator in a terminating exchange having need for a line circuit from the tandem exchange to another terminating exchange ordinarily must make an attempt to gain access to such a line circuit regardlessly of whether all of the line circuits to the other terminating exchange are in use. In the instances where the operator receives busy indication when attempting to appropriate a line circuit of a group, she must make one or more'further attempts until a free line circuit is obtained.

Such repeated unsuccessful attempts result in loss of operator time and the useless occupying of inter-exchange circuit facilities.

It is an object of the invention to overcome the above described deficiency in inter-exchange line circuit operation by providing a new and novel line circuit group busying arrangement wherein a group busy signal, related to a group of line circuits from a tandem exchange to a terminating exchange, is located in each other terminating exchange having access to said related line circuit group, and this group busy signal is operated Whenever all the line circuits of said group of line circuits are simultaneously occupied.

A feature of the invention resides in the novel manner in which a line circuit group busy signal in a terminating exchange is operated from the tandem exchange over one of the regular line circuits from the tandem exchange to the terminating exchange.

Another feature of the invention relates to the provision of more than one line circuit group busy signal in a terminating exchange for giving group busy supervision of more than one line circuit group from the tandem exchange to more than one other terminating exchange, over a line circuit, or circuits, of the group from the tandem exchange to the first mentioned terminating exchange in a new and novel manner.

A further feature of the invention concerns a novel circuit arrangement wherein the superimposition of an alternating current of a nonvoice frequency on a line circuit from the tanthe operation of a busy signal in the terminating exchange.

There are other objects and features of the invention'having to do for the most part with the circuit details necessary to carry out the foregoing.

The various objects and features of the invention will be understood best from a perusal of the following description of the drawings comprising Figs. 1 and 2, which show by means of the usual circuit diagrams a suicient amount of apparatus to enable the invention to be describedA and understood. Y

Referring now to the drawings- Fig.v l is a single-line circuit diagram showing a tandem exchange A having line circuits extending to three terminating exchanges B, C and D, and also means for enabling calls initiated in the tandem exchange and in any of the termi-A nating exchanges to seize a line circuit to one of the terminating exchanges.

Fig. 2 shows the tandem exchange, the three terminating exchanges, and the line circuits of Fig. 1 and, in addition, means for applying an alternating current, or currents, to certain of the line circuits for causing the operation of related busy signals in the terminating oflices.

Two'line circuits are shown in Figs. l and 2 from the tandem exchangeA to each of theY terminating'exchanges, line circuits for terminating exchange B being designated by the reference characters I0 and I5, for terminating exchange C by the characters 20 and 25, and for terminating exchange D by the characters 30 and 35. It should be understood, however, that any required number of line circuits may be provided between the tandem exchange and each terminating exchange.

Line circuit I0 terminates at the tandem exchange A in a line equipment I2 and at terminating exchange Bin a line equipment I I. Similarly, line circuit I5 terminates in line equipments I4 and I3 respectively at the tandem exchange and terminating exchange B: line circuits 20 and 25 terminate respectively in line equipments 22 and 24 at the tandem exchange and in line equipments 2| and 23 at terminating exchange C; and line circuits 30 and 35 termi-- nate respectively in line equipments 32 and 34 at the tandem exchange and in line equipments 3I and 33 at terminating exchange D. These line equipments may be of any well-known type and circuit arrangement, according to preference or requirement and, therefore, it is condeni exchange to a terminating exchange causes, Il sidered unnecessary todetail any particular arrangement in this disclosure. In Fig. 2 for the tandem exchange end, enough of a chain circuit arrangement is shown associated with the line equipments yofthe line circuits for each terminat-k ing exchange to properly Ydemonstrate the functioning of the line circuit group busy supervision.

. The line the tandem exchange A (Fig. 1) may be of any conventional type of selector switch, but as deand automatic rotary movement. These line circuit selectorsl have one level of bank contacts multiplied together for each terminating exchange, and contacts in each bank level 'are con,- nected to the line circuits from thetandem exV changeto the related terminating exchange. It should be understood at this time that While only one line-circuit selector is shown in Fig. 1 for each ofthe four exchanges, line circuit selectors are provided for each exchange according to traine requirements. v c J v Y The Yselection units .1, I1, 21 and .31 eachree spectively represent any desired` train of conventional switches required in the related eX- circuit selectors s, is, 2s and se 5in AY pictedcomprise the Well-known Strower Selettor switch having controlled vertical movement f .4rv Y Y B wishes to extend a connection to exchange C, then by means of thepositional equipment (not shown) of Yoperator unit I8 (Fig. 1) the operator controls the switchtrain represented by selection unit I1 to select a free outgoing line selector in the tandem exchange A, which Vfree selector is now assumed to be selector I-9 reached `over line circuit I5. Next,` the operator controls selectorV I9 (by dialing the digit 2.). toV raise the associated shaft and wipers of selector' I-B' to then second level whereupon selector I9 then automatically rotates of the selector, bank,

its, wipers into the second level ofthe `bank in VAa 'well-known manner. I'f line Ycircuit 20 out-r going vfrom tandemfexchange A to terminating exchange C lis notin use at this time, then the j Wipers .of selector I9 willstop on the first conchanges for selecting' a free linecircuit selector in the tandem exchange as represented by the reference vcharactersV 9,' I9,V 29 or 39. Since the present invention is'notconcerned with the deV tails of such selection units or trains, it is considered unnecessary to include furtherl details of Y In the instance of these operator units also, thepresent invention is not concerned withthe exact details o f the operator positions and related positional control equipment arrangements,"it`

being understood that .any well-known or conventional arrangement may be utilized. The alternating current source 51 (Fig. 2) may be of anyV well-known type of generating equipment'capable of producing currents of at least two, frequencies. It should be understood, how'- ever, that the two frequencies indicatedv for the generating equipment in Fig. 2 are for explanatory purposes only and do' not impose any par-'- ticular limitations or restrictions. n

The filters indicated by the reference characters 6I, 62, 63, (i4,` 65, 66, 10,'15, 80, `85, 90 and 95 in Fig. 2 may be of any well-known type of lter tuned Yto pass alternating current of a particular frequency. AsA in the ease of the alternating current generating equipment, the frequencies indicated for the variousr filters are for explanatory purposes only and 'correspondingly do-not impose any particular limitationsv or restrictions. The busy signal equipments 1I, 16, 8|,186,'9I and 96 in Fig. 2 each comprise any suitable'arrangement of equipment and circuit arrangement capable of responding to an input of alternating Y current (supplied bythe related filter* 10, 15, 80;

85, 90 or 95) and as a'result of'such response then causing the operation oflthe related busy signal 12,1182, 81,92 and 91. Y

Having described the equipment and appara--v tus, a detailed description of the operation will nowbe given. 'i i y'Assuming iirst` that enoperator in exchange tacts ofthe second level of the bank, and the operator equipment represented by unit VI8 is automatically connected to line circuit'20, 'also in a V"well-known manner. If, however, line circuit-201s inv prior vuse. at Vthe time selector V |19 tests'fth'e first contacts of the second level of thef'bank, theny the Wipers ofV selectorV L8 are automatically Arotated tothe second contact of exchange-Chanalternatively control selector 29.A

to select either `line circuit 30 or 35-outgoing from 'tandemfv exchangefA to terminating exchangelD by dialing the digit 1 selector 29 to raise' its wipers to the firstV level ofthe switch bank.' VIt' will also be apparent that 'an'operator in exchange C can controlselector 29 in tandem exchange A (over line'ci'rcuit'ZIi)V to select either line circuits I0 or I5 to terminating exchange B','or to select either line circuits 30v or 35 to terminating exchange D: that an operator in Yexchange D canf control selector 39 in tandem exchange VA(over line circuitr36) to Select either lineV circuits I0 orvI5'to terminating exchange B, or toselect either line circuits '20 Gr.25 to terminating Yexchangel C; and that an y operator in tandem exchange A Vcan Y control outgoing 4from"tandern'exchange A to terminating;

Selector. y9 (over line circuit l)Y to select eitherV line circuits III or I5 to,Y terminating exchange connect with line circuit `ISjthenrthe chain re- V layer.; and 45 in line equipmentslz and I4 (Fig. 2)"arev operated ina well-known manner to com-'- plete an obvious circuit to relay 40, causing relayl el)V to operate. Int armatures 4I and 142,'relay lilY extendstheA alternating current Supply fromgenthese'ffilters are tunedto pass alternating current of 11 0,000' 'cycle frequency; filter 63,'there,fore, causing the alternating currentroflooo Ycycle Y frequency to fbesuperimposed on linecircuit 25 exchange' C, and lter N causing the alternating and thereby cause' 1 current of 10,000 cycle frequency to be superimposed on line circuit 30 outgoing from tandem exchange A to terminating exchange D.

Filter 80 in bridge of line circuit 25 at exchange C is tuned to pass alternating current of 10,000 cycle frequency and, therefore, causes the alternating current superimposed on line circuit 25 by means of filter 63 to be extended to busy signal equipment 48|. Means (not shown) associated with busy signal equipmenty 8| responds to the impressed alternating current in a well-known manner, and other means (not shown) also associated with busy signal equipment 8| responsive to the action of said first means of busy signal equipment 8| causes ground potential to be extended to busy signal 82 thereby to complete the' circuit of busy signal B2. The glowing of busy signal 82 indicates to the operator, or operators, at exchange C that al1 of the line circuits (l0 and l5) outgoing from the tandem exchange to terminating exchange B are in use. Now should a demand for a connection from exchange C to exchange B be initiated while line circuits l and I are in prior use, it will be unnecessary for an operator at exchange C to attempt to select a line circuit from tandem exchange A to exchange B until busy signal 82 ceases to glow. Operator time which would otherwise be expended in repeated testing is conserved, and useless occupations of line ycircuits from exchange C to tandem exchange A are avoided.

Filter S0 in bridge of line circuit 30 at exchange D is also tuned to pass alternating current of 10,000 cycle frequency, and therefore, causes the alternating current superimposed on line circuit 30 by means of lter 64 to be extended to busy signal equipment 9|. As a result of the passing of 10,000 cycle alternating current to busy signal equipment 9|, busy signal 92 is caused to glow in a manner similar to that described in the preceding paragraph for the glowing of busy signal 82 at exchange C. The glowing of busy signal 92 indicates to the operator, or operators, at exchange D that all of the line circuits (I0 and I5) outgoing from tandem exchange A to terminating exchange B are in use. As a consequence of this group busy supervision at exchange D, the conservation of operator time and the eicient occupation of the line circuits from exchange D to tandem exchange A become realities.

Assuming now that line circuits and 25 outgoing from tandem exchange A to terminating exchange B are in use instead of line circuits I0 and I5, then the chain relays 50 and 52 in line equipments 22 and 24 at tandem exchange A are operated in a well-known manner to complete an obvious circuit to relay 41, causing relay 41 to operate. At armatures 48 and 49, relay 41 extends the alternating current supply from generator 5 to filters 5| and 65 in multiple. Filter 6| is tuned to pass alternating current of 10,000 cycle frequency but not alternating current of 12,000 cycle frequency. Filter 55 is tuned to pass alternating current of 12,000 cycle frequency but not alternating current of 10,000 cycle frequency. Filter 6|, therefore, causes 10,000 cycle alternating current to be superimposed on line circuit I5 outgoing from tandem exchange A to terminating exchange B, and lter 65 causes 12,000 cycle alternating current to be superimposed on line circuit outgoing from tandem exchange A to terminating exchange D. Filter 10 in bridge of line circuit I5 at exchange B is tuned to pass alternating current of 10,000 cycle frequency and, therefore, causes the 10,000 cycle alternating currentl superimposed on line circuit I5 by means of filter 8| to be extended to busy signal equipment 1I, which functions (in the manner similar to that previously described for busy signal equipment 8|) to cause the glowing of busy signal 12. The operators at exchange B are thuswise informed that all of the line circuits (20 and 25) outgoing from tandem exchange A to terminating exchange C are in use. Filter 95 in bridge of line circuit 30 at exchange D is tuned to pass alternating current o1 12,000 cycle frequency and, therefore, causes the 12,000 cycle alternating current superimposed on line circuit 30 by means of lter to be extended to busy signal equipment $5 which functions (in the manner previously described for busy signal equipment 8|) to cause the glowing of busy signal 91. The operators at exchange D are thuswise informed that all of the line circuits (20 and 25) outgoing from tandem exchange A to terminating exchange C are in use.

It will also be apparent that when line circuits 30 and 35 outgoing from tandem exchange A to terminating exchange D are in use, filter 15 in exchange B will pass 12,000 cycle alternating current to busy signal equipment 16 thereby to cause the glowing of busy signal 11, and lter 85 in exchange C will pass 12,000 cycle alternating current to busy signal equipment 86 thereby to cause the glowing of busy signal 81.

It will be further apparent that the line circuits outgoing from tandem exchange A to any two of the terminating exchanges B, C and D may be in use at the same time and, therefore, there will be both 10,000 cycle and 12,000 cycle alternating current superimposed on one of the line circuits outgoing from tandem exchange A to the remaining third terminating exchange. Assuming now that the third terminating exchange is exchange B, then lter 10 will pass 10,000 cycle alternating current to busy signal equipment 1| but not 12,000 cycle alternating current, and iilter 15 will pass 12,000 cycle alternating current to busy signal equipment 16 but not 10,000 cycle alternating current. As a consequence of the functioning of busy signal equipments 1I and 15, busy signals 12 and 11 glow to respectively indicate that all of the line circuits outgoing from tandem exchange A to terminating exchanges C and D are in use.

The frequencies of alternating current indicated in Fig. 2 are well above the upper cut-01T point of ordinary voice currents and, therefore, are superimposed on a line circuit outgoing from tandem exchange A to any one of the terminating exchanges regardlessly of whether the particular line circuit is already in use on a telephone conversation.

It should be understood that while one embodiment of the present invention is disclosed and described in the preceding specification, the invention is not limited to the particular form or application shown, but is entitled to the equivalents thereof within the scope of the appended claims.

I claim:

1. In a telephone system, first and second terminating exchanges, a tandem exchange, lines from said tandem exchange to both said terminating exchanges, said lines to said rst exchange accessible to calls initiated in said tandem exchange or said second exchange, said lines to said second exchange accessible to calls initiated in said tandem exchange or said first exchange, a source of alternating current, a supervisory signal in each said terminating exchange, means responsive to a simultaneous occupancy of all said lines to oneV of said terminating exchanges for causing the superimposition of said alternating current on one ofsaidlines to said other terminating exchange, and means responsive to said superiinposition of said alternating current for causing the supervisory signalin said other terminating exchange to function, thereby to indicate in said other terminating exchange that all said lines to said one terminating exchange are occupied. i

2. InA a telephone system as claimed in claim l wherein said source of alternating current is of a non-voice current frequency.

3. In a telephone system, rst and second terminating exchanges, a tandem exchange, lines from said tandem-exchange'to each said first and second exchanges, means for connecting calls initiated in said tandem exchange to idle ones or" said lines to either said first or said second exchange, means ior connecting calls initiated in said iirst exchange to idie ones of said lines to said second exchange, means for connecting calls initiated in said second exchange to` idle ones of said lines to said iirst exchange, a source of non-voice frequency alternating current, a chain circuit common to said lines to one of the terminating exchanges operative when all said lines to said one terminating exchange are inruse, a j

supervisory signal in the other terminating exchange, means responsive to an operation of said chain circuit forV superimposng said alternating current on one o the lines to said other terminating exchange, and means responsive to said superimposing of said alternating current for causing said supervisory signal to operate and thereby indicate that all said lines to said one terminating exchange are in use.. l

4. In a telephone system as claimed in claims wherein said means responsive to an` operation oi said chain circuit comprises a lter tunedA to pass said alternating current. Y Y

in a telephone system as claimed in claim 3 wherein said means responsive to anY operation of said chain `Circuit comprising a filter tuned toY pass said aiternating current,y and wherein said means responsive to said superimposing of said alternating current includes a filter tuned to pass said superimposed current.

caracas d. In a telephone system, a plurality of termihating oifices, a tandem office, trunlrsfrom said tandeinof'ce to each of said terminating oces; means ior completing calls between saidterminating offices over said trunks from said tandem oflice to said terminating offices, a source of nonvoice frequency alternating current, achain circuit cominon to the trunks from said tandem oce to one of said terminating oiiices operative when said trunks to said one terminating oiice becomes busy, a Vlter associated with one of said trunks from said tandem office to each oiy said other terminatingoices, said filters tuned to pass said alternating current, a signal in each of said Yother terminating oiices, means responsive to an operation of said chain circuit for connecting said alternating current to. each ofl said filters thereby to cause each saidV filterv to extendy said alternating current toits associated trunk,

and means in each said associatedtrunk` responsive tcsaid extension of said alternating current for causing. saidisig-nal in eachv of said other` terminating oces to operate, therebytoindicate in all said other ofiices` that allv ci said trunks from said tandem office: to said one terminating olce are busy. 7. In a telephone systemsfirsasecondand third terminating oices, a tandem oice, lines from saidy Vtandem oce to eachof said termina.tingY oices. means. for completing-calls from saidY tandem oiic'e tof said;v terminating offices over saidVY lines, means for. completing;I callsY between` said terminating. oices Vover said lines, alternating currents of two dierent frequencies, means rei sponsiveto a simultaneous occupancy of. all the lines to said rst terminating. cnice for. superimposing saidv alternating. current of. one of saidlirequencies ion one of the lines to saidsecond terminating.. offlce'and for superimposing said alternating current ofsaidother frequency on'one of theiines to said third'. terminating oflice, afsigmtl'V in each o said second and third terminating f oiiices, means responsive' to saidl super-im'posingv of. said one frequency for Yope'ratingsaidsignalin saidsecond.` terminating o'ice, means responsive g to.v saidv superrnposing. of said other frequency for operating said signal; in said third terminating office, saidvoperations. of saidtWo signals indicat-ing in said second and third terminating. olces respectively that'V all thel lines from; said'tandem office t0 said .nrst terminating oflice. arev inthe .occupied position.

8. The telephone systemv asclaimed in claim 7 wherein theV two different frequenciesof saidY alternating currents `are. above the: rangefoffvoice lines from said Aoice tofsaidB; C and Domces,

means for completing, calls from said A oice to. said B, C and D officesover said lines, means' for completingv callsbetween said. B, C and D oflces over saidy lines, alternating currents. of twodifferent frequencies, means. for superimposing said alternating current ofl one of'said frequencies on one ofY said lines. to said yJD office when all said linesto said `IB oiIicebecome busy, means for superimposing said alternatingcurrent ofi-said other frequency on. said one-line tol said D ollice when all saidlines to said C oiice become busy,v two busy signals insaid D office,A means responsive to a superimposingfof said one frequency onsaid one line to said D office for-causing. one: of

said` busy signals tofunction, andy means responsiveto a superimposing of. said other frequency oni said one linel tosaidD` office for causing saidy other. busy signal to function.r f'

l0. The telephone system asclaimedin claim 9. wherein said means. for supe-rimposingk said alterhating.v current of said oneV frequency includes a frequency includes a lter. tuned. to pass saidv Y other frequency but. notsaid one frequency..

GEORGE W'. MITCHELL.

N o referencescite'd.v

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