US1919317A - Telephone system - Google Patents

Description

July 25, 1933- J. A. BURGENER TELEPHONE SYSTEM Filed Dec. 29. 1931 Patented July 25, 1933 UNlTED STATES.

PATENT oFFlcE..

Jomr A. BUBGENB., or nINsDALn. ILLINOIS, AssIe'Non, BY MESNE- ASSIGNMENTS; To

.ASSOCIATED-ELECTRIC LABORATORIES, INC., OF CHICAGO,

TION 0F DELAWARE TELEPHONE SYSTEM Application led December 29', 1981. Serial No. 583,667.

The present invention relates to telephone systems in general, but is more particularly concerned with telephone systems wherein the subscribers lines are classified and where in provisions are made for informing the telephone operator answering a call of the class to which the calling line belongs; and the main object, broadly stated, is to provide a more refined and satisfactory arrangement for notifying the operator of the class in.

which the calling line belongs.l

General description connection to a manual switchboard by Way of a trunk line leading from the automatic switchboard to the manual switchboard, the manual operator is signalled; while, at the same time, the release trunk conductor ofthe connection established from the calling line to the automatic-to-manual trunk line is in ductively coupled with the talking circuit, so that, when the operator answers, any tone current placed on the release-trunk conductor of the established connection by way of the subscribers individual line equipment is heard by the operator fora predetermined interval of time after the operator responds. Now, it often happens during certain s ocalled busy periods that the manual operator is unable to respond promptly, with the result that several unanswered connections may extend to her switchboard at the same time. With the tone current being simultaneously applied to several of the interswitchboard trunk lines, which are often eX- teuded from one ofiice to another, and therefore of considerable length, some diiiculty is experienced in preventing the tone current from being induced in the parallel trunk lines Y which conversation is being carried out may become of annoying magnitude when tone current is'being continuously applied to several trunk lines over which unanswered connections have been extended to the manual switchboard. If the ap lication of tone'current to an inter-switch oard trunk line is made lonly after the operator responds and then only for a long enough time to enable the operator to distmguish the character of application of the distinctive tone current to the inter-switchboard trunk line responsive to the-call being answered by the operator and for automatically discontinuing the application of tone current at the end of a predetermined interval long enough to enable the operator to distinguish the character of the tone signal;

It is understood, of course, that systems have been developed heretofore wherein the applica tion ofA tone current to the interswitchboard trunk line is made only after the operator responds and is terminated after the operator has heard and distinguished the characteristic tone signal; but, as ar as applicant is aware, this is the first time that this operation has been performed entirely automatically responsive to the simple answering act of the operator performed in the usual manner and without necessitatin a special key manipulation or other simi ar special acts on the part of the operator to initiate or terminate the application of the tone current.

Description of drawing Referring now to the accompanying single sheet of drawing, the showing therein is similar to the showing in the drawings in the Tharp application hereinbefore referred to; the main difference lies in the arrangement employed in the .so-called repeater or trunk circuit TC connected on the automaticswitchboard end of the inter-switchboard trunk line comprising conductors 23 and 24.

minates at the manual switchboard in a jack;

such as the jack J, illustrated, and each trunk line has a line circuit associated therewith at the switchboard, suchas the line circuit LC. A number of cord circuits, such as the cord circuit CC, are provided, which cord circuits are preferably o f the general type disclosed in Patent No. 1,802,449, granted April 28, 1931 to A. W. Steinke.

It will be noted that two tone sources are shown associated with the lineswitch LS, the

tone transformers 25 and 26. The operating Acurrent for the operating magnet 1 of the lineswitch LS may be obtained through the secondary winding of either tone transformer dependingupon the class-in which the line of substation A belongs'. As shown, the operating current for the lineswitch magnet is obtained'through the secondary winding of the transformer 25, through which the first of the two characteristic tones is supplied, denoting that the line of sub-v station A belongs in the first class. -It Will be understood, of course, that the number of classes may be extended as desired by providing additional tone sources.

Detailed description The invention having been described generally, a detailed description of the operation of the apparatus shown will now be given.' For this purpose it will be assumed that the subscriber at substation A removes his receiver and dials the digit assigned to the manual switchboard for the purpose of soliciting the aid of the manual operator in establishing a connection which may not be established directly through the automatic switchboard.

Seizing the truck circuit T0 When the receiver is removed at substation A, the line relay 3 of the lineswitch LS operates in theusual manner and connects up the magnet 1 for operation, at the same time enabling switching relay 2 to operate (as soon as an idle trunk is found) and extend a connection by way of wipers 4 to 6 to thistrunk. Assuming that the vtrunk line extending to the selector S is the first one found to be idle, the selector S is seized and thereupon prepared for operation in the usual manner.

, When the digit assigned to thefswitch-v backbridge relay 11', operates over the calling line and closes a circuit for release relay 12 at its upper armature, at the same time reversing the connections between the windings of back-bridge relay 11 and the talking conductors. .When release relay 12 responds to the closure of its circuit, it places a ground potential on the incoming release trunk conductor 8 by Way of the upper winding of the 'induction coil 14, thereby providin a holding circuit for the switches LS and Signalling the operator Release relay l2 also places a ground poten-A tial on conductor 4 1, thereby closing a circuit through contacts of relay 17 for the ringing-start relay 15. Relay 15 thereupon operates and locks itself -to conductor'41 by Way of the middle-upper armature of relay 11, at the same time, applying ringing current to the trunk conductors 23 and 24 at its upper and lower armatures, by way of the corresponding armatures of relay 17. At the same time, the placing of ground potential on conductor 41 results in the closure of a circuit through contacts of relay 17 for the timer relay 16. Relay 16 thereupon operates and closes acircuit for relay 17 by Way of contacts of the latter relay. Relay 17 does not respond immediately to the closure of this circuit, because relay 16 is a vibrating-con tact relay, having a weight attached to the contact thereof which causes the contact to vibrate for an interval before a continuous connection is made.

Stop-ping the flow of ringing current As soon as the contact of relay 16 has ceased to vibrate, relay 17 operates and locks itself to conductor 41; disconnects relay 16 from conductor 41 and prepares a new circuit for it,

whel upon relay 16 deenergizes; disconnects the ringing current and closes points in the talking circuit at its upper and lower armatransfers the vibrating contact of relay 16 from its own winding to the winding of thev ico tures; and at its inner-lower armature it .The ringin flow of current has now been discontinued y the operation of relay 17, but relay 15 remains operated in spite of the lopening of its initial circuit at contact of relay 17, because of the above-mentioned-locking circuit established for this relay through its own inner-upper contacts by Way of middle-upper armature of4 back-bridge relay 1 1 and conductor41, grounded at contacts of relay 12. l

With relay 15 operated, a characteristic ring-back tone is placed on the lower talking conductor from the ring-backtone conductor 27, indicating to the calling subscriber that the operator 1s now being signalled.

In the manual office, the above-described momentary application of ringi-ng current to the trunk line causes an operation of the line relay 18, whose upper Winding is'normally included in a bridge circuit across the talking conductors of the trunk line. Upon o erating, relay 18 closes a locking circuit or its lower winding at its lower contacts, and at its upper contacts it closes a circuit for the lamp L to signal the operator.

T he operator answers The operator responds Vto the lighting of the lamp L by insertin the plug of an idle cord circuit, the plug of the cord circuit CC for example, into the jack J. When this energizes over the talking conductors of the trunk line in series with back-bridge relay 11 of the trunk circuit TC. With relays 2O and 21 operated, a circuit is closed through contacts of both relays for the connecting relay 22, which operates to connect the operators headset conductors 29 and 30 across the talking strands of the cord circuit.

Apply/ng the class-tone current In the trunk circuit TC, when back-bridge relay 1l energizes over the trunk line 1n series with'the polarized supervisory relay 21 of the cord circuit CC, it reverses the connections between the incoming talking conductors 7 land 9 and the windings of line relay 10 for the purpose of transmittingback a supervisory signal which is of utility in certain cases, as is well known.

Back-bridge relay 11 also closes a multiple holding circuit for release relay 12 at its inner-upper armature; and at its middle-upper armature it opens the locking circuit of the ring-start relay 15 'and closes a new cir.

vcuit for timer relay 16. T-he ring-start relay 15 n'ow falls back and terminates the application of ring-back-tone current to the lower talking conductor 'to indicate to the subscriber that the operator has responded. The new circuit for relay 16 closed by contacts of relay 11 includes. the o erated inner-upper armature of relay 17. hen relay 16 operates at this time it closes a circuit through' the operated inner-lower armature of relay 17 for thetone-cut-o relay4 13, which relay does not operatefor the time being because of the time interval required for the vibrate ing Contact of the timer relay to stop its vibration. and make continuous contact. As a further result of the operation of back-bridge relay 13, the direct ground cony nection normally applied to the right-hand terminal of the lower winding .of relayll is replaced by a ground connection through the inner-lower armature of relay 11, normally closed contacts controlled by thevarmature of the tone-cut-off relay 13, and the lower winding of the induction coil v14. By this connection, the 'characteristic tone current flowing fromgthe secondary winding of the transformer 25 and through the operating magnet 1 and associated relay 2 to the release trunk conductor of the established connection and thence to ground by Way of the upper winding of the induction coil 14 causes a characteristictone current to flow to the talking circuit by yway of the lower winding of the induction coil 14 and the` lower winding of the back-bridge relay 11. The 'tone produced by this flow of current may be heard by the subscriber at substation A a'nd also by the operator, whereby the operator learns what class the calling line is in.

Terminating the claas-tone current After the interval for which it is adjusted, the vibrating Contact of the timer relay 16 ceases to vibrate, whereupon the tone-cut-oif relay 13 responds and re-applies ground potential directly tothe rightha'nd terminal of the lower winding of back-bridge relay 11', at the same time open-circuiting the lower winding of the induction coil 14.

The momentary application ofthe distinci tive tone current has been terminated, and the subscriber and operator ma now converse with each other as desire following which the connection may be further ext-ended by Way of the cord circuitCC, in which case the relay 22 is caused to fall back and disconnect the operators headset conductors from the talking strands of the cord circuit.

Repeating they tonevaignal In case vthe operator wishes to verify the tone signal initially heard, he may cause the tone signal to be repeated by merely removing the plug P momentarily from the "ack J A and again inserting the plug. The e ect of Releasing the established connection After the subscriber at substation A has replaced his receiver and caused the operator to receive a disconnect signal at the lamp controlled by the battery feed relay 21, when the connections to the back-bridge relay 11 are reversed, and the .operator has removed the plug P from the jack J and allowed the back-bridge relay 11 of the trunk circuit TC to restore, the circuit of release relay 12 is finally opened, whereupon relay 12 falls back and pei'mitsrelays 13, 16, and 17 to restore, at the saine time disconnecting ground potential from conductor-8 to permit the selector S to release and the lineswitch LS to restore to normal condition.

- lVhat is claimed is:

1. In a telephone system, a subscribers line identified by a distinctive tone, a trunk line, means for extending a call from said subscribers line to the trunk line, means for answering the call, and means for applying said tone to the trunk line and for removing thel same responsive to the answering of the ca 2. In a telephone system, a \subscribers line, a source of tone associated with said line, a trunk line, means for extending a call from said subscribers line to said trunk line, means for answering the call, means operative for connecting said tone source to the trunk line and for subsequently disabling the tone source, and means responsive to the answering of the call for operating said last means. v

3. In a telephone system, two exchanges, an interconnecting trunk line, means in one exchange for extending a call to the other exchange via said trunk line, means inthe other exchange for answering the call, a source of tone in said one exchange, and means responsive to the answering of the call for momentarily applying tone from said source to the trunk line and for then terminating the application. v

4. In a telephone system, two exchanges, an interconnecting trunk line, means in one exchange for extending a call to the other exchange via said trunk line, a link circuit in said other exchange for answering and further extending the call, a source of tone in said one exchange. and means responsive solel -to the connection of said link to the trun line toanswer the call for connecting said tone source to the trunk line and for disconnecting it at the end of a predetermined interval.

5. In a telephone system, a trunk line con-- nectin an automatic exchange and a manual switch card, subscribers lines of different classes in the automatic exchange, the lines of each class being identified by a separatev tone supplied by tone sources associated with the lines, means for extending a connection from a calling line to the switchboard via said trunk line, a link circuit at the switchboard adapted to connect with the trunk line for answering the call, and means wherebyv v-tors and for then` disconnecting them at the end of a short interval.

7. In a telephone system, a trunk `line extending from a first switchboard to a second switchboard, said second switchboard being a manual switchboard, means at the first switchboard for extending a connection to said trunk line and for signalling the operator at the second switchboard over said trunk line, means under the control of the operator at the second switchboard whereby the operator can respond to the said signal `by placing herself -in telephonie communication with the trunk line, means also responsive to the last named means for setting up a supervisory condition over said trunk line, means at the first switchboard for making a momentary characteristic application of tone current to said trunk line, and means respon-V sive to said supervisory condition being set up for initiating the operation of the lastnamed means.

8. In a telephone system, a line identified by a distinctive tone, a trunk line extending to a manual switchboard, means for extending a call from said line to said trunk line, means including a plug and a jack at said switchboard for answering said call, and means responsive to the insertion of the plug into the jack pursuant to the answering of the call for initiating and terminating a momen- JOHN A. BURGENER.

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