US2315378A - Automatic telephone system - Google Patents

Description

March 30,1943. w. T. POWELL 2,315,378

AUTOMATIC TELEPHONE SYSTEM Fi'ld Sept. 13, 1940 10 Sheets-Sheet 1 INVENT OR.

Wl/VFZED 72' POWELL A ORNEY.

30, 1943. w. 'r. POWELL 2,315,378

AUTOMATIC TELEPHONE SYSTEM V Filegi Sept. 13, 1940 1Q Sheets-Sheet 2 I? I INVENTOR.

WIN/2E0 7: POM Ell ATTORNEY.

- March 30, 1943.

POWELL AUTOMATIC TELEPHONE SYSTEM Filed se tnls, 19 1b 1 .O Sheets-Sheet 3 "A I OR-NEY.

March 30, 1943. w. POW L 2,315,378 v I I AUTOMATIC TELEPHONE SYSTEM Filed Sept. 13, 1940 10 Sheets-Sheet 4 l J H I i LINE H l we T r .m 173 1 27.4

I T I175 l L A l 208 207 I am y l 3 n I v l 3 205 I EN. i Bill/5N. M 04 206 (-n H INVENTOR.

W/IVFEED 7'. POWELL A ORNEY.

March 30, 1943.

W. T. POWELL Filed Sept. 13, 1940 AUTOMATIC TELEPHONE SYSTEM 10 Sheets-Sheet 5 Wl/VFPED 7'. POWELL ATTORNEY.

March 30, 1943.

Filed Sept 1 w. T., POWELL AUTOMATIC TELEPHONE SYSTEM 15, 1940 10 Sheets-Sheet 6 1 mvmom W/NFEED Z POWELL 30,1943. w. -T, aws; 2,315,378 I AUTOMATIC TELEPHONE SYSNTEM Filed Sept. 13, 1940 1 o Sheets-Sheet v I EEV. 2/176 TONE I 63 a) m,-1 I I isY l "ATTORNEY.

March so, 1943. I w.1". POWELL JJ {2,315,378 AUTOMATIC TELEPHONE SYSTEM "'Fil'ed Sept}. 13. 1940 10 She ets-Sheet s D/FFEPENT/FL INVENTORQ W/NFEED Z" POW n .8 F 42% I AI*ORNEY.

March 30, 1943. v w, 1', p 'wE 2,315,378

AUTOMATIQ TELEPHONE SYSTEM Filed Sept. 13, 1940 l0 Sheets-Sheet 9 INVENTOR.

W/NFRED r POWLL A ORNEY.

March 1943- w. r. POWELL 2,315,378

AUTOMAT IC TELEPHONE SYSTEM Filed Sept. 13, 1940 10 Sheets-Sheet l0 INVENTOR. 1 [0 WM/Fem z POWELL BY A I A ZTTORNEY.

Patented Mar. 30, 1943 AUTOMATIC TELEPHONE SYSTEM Winfred T. Powell, Rochester, N. Y., assignor to The Stromberg-Carlson Telephone Manufacturing Company, Rochester, N. Y., a corporation of New York Application September 13, 1940, Serial No. 356,623

6' Claims.

This invention relates to telephone systems and more particularly to automatic telephone systems.

Present automatic telephone systems, are commonly so arranged that it is necessary for the calling party when calling another subscriber on his own line to dial a difierent number from that by which the wanted party thereon is usually called. Such an arrangement for handling revertive calls is confusing to the subscriber and results in many false calls.

In accordance with the present invention, a novel arrangement is provided wherein certain means discriminates between an ordinary busy line and a busy line due to a revertive call thereon while dialing the same called line number in the case of a revertive call as in the case of. a normal call. This discriminating means in the first instance prevents the signalling of the'busy wanted line but in the second instance permits the wanted subscriber, in the case of the revertive call, to be signalled during the period that the calling subscriber temporarily hangs up his receiver in accordance with instructions.

Another feature of the invention relates to an arrangement whereby a series of counting relays in addition to effecting the selecting operation of the connector also selectively controls the application of selective ringing current to the called subscribers line.

Still a further feature of the invention relates to a novel arrangement for intercepting preliminary impulses.

The various features and advantages of the invention will appear from the detailed description and claims when taken with the drawings which diagrammatically represent the automatic telephone system of the present invention, when ar ranged with Figs. 1, 2, 3 and 4 in a horizontal row and with Figs. 5, 6, 7, 8, 9 and 10 arranged in a second horizontal row in the, order named, the upper margins of Fig. 5 matching with the lower margin of Fig. 1. In Figs. 1 and 5 there is illustrated a calling telephone line and the lockout arrangement common to a group of telephone lines; Figs. 2 and 6 represent a group of finder relays for connecting a link circuit to a calling telephone line; Figs. 7, 8 and 9 illustrate a link circuit and the counting relays associated therewith; the righthand portion of Fig. 9 and Fig. 10 illustrate a relay connector for connecting a link to a wanted telephone line; Figs. 3 and 4 represent a trunking arrangement whereby a call maybe extended to or received from a trunk connected to a distant office.

It is believed that the inventionwill best be understood by describing the operations involved in extending a telephone call from a calling subscribers substation #221 to a called subscribers substation #214. When the calling subscriber at substation #221 originates a call by removing his receiver from its switchhook, a circuit is completed for the line'relay II] from the negative pole of battery, upper winding of this relay, back contact and armature of the cutoff relay I I, upper side I2 of the calling subscribers line thru the calling subscribers substation network, lower side of the calling subscribers line l3, lower winding of the relay Ill, lower back contact and armature of the cutoff relay II, to the positive pole of battery. In the form of the system herein disclosed, there is provided a lookout relay arrangement whereby only one callingsubscriber at a time can extend his line to an idle link circuit. This locking relay arrangement comprises twenty tens lockout relays (of which only ten are completely illustrated, the twentieth tens relay being shown in dotted lines) and ten units lockout relays. When the line relay III is energized, a lockout circuit is completed from the negative pole of battery, resistance 26,,continu-- ity and back contact of relays/TI to TIU inclusive, conductor I5, back contact, continuity spring and winding of the second tens lockout relay I6,

conduotor II, innermost back contact and armature of the slow releasing relay I8, armature and front contact of the linerelay Ill, middle arma-- ture and back contact of relay I8, conductor 20, the first units lockout relay 2I, continuity spring and back contact of this relay, conductor 22, back contact and continuity spring of relays UIU to UI inclusive, to the positive pole of battery. The tens lockout relay i6 and the units lockout relay 2| are operated over the above described circuit, each of which closes a locking circuit for itself and opens the operating circuit for the others in the corresponding group. Thus the tens relay I6 and the units relay 2i are locked operated until the callingline is extended to an idle link circuit. It will be understood that while thetens relay and the units relay are, operated, no other tens or units relays cangbe operated,

since their energizing circuits will be interrupted by the tens lockout relay and the units lockout relay then operated.

Alarm relay I4, which is normally energized except when a call is being extended by the lockout relays, functions whendeenergize-d to close an alarm circuit. This alarm circuitlbecomes efiective when the relay I4 is deenergized for a period longer than that normally necessary to extend a calling line to a link. Alarm relay 23 functions in like manner in connection with the units lockout relays to close an alarm circuit when an operated one of these relays fails to release Within a short interval of time.

As soon as the tens lockout relay l5 and the units lockout relay 2| have been energized and locked operated in the manner just described, the tens finder relay and the units finder relay of an allotted link circuit function to connect this allotted link to the calling line. Let it be assumed that the first link of this series is allotted for use and under this condition the slow releasin allotter relay 2'! is operated from the negative pole of battery, winding of this relay, upper back contact and armature of the relay 28, conductor 29, front contact and armature 35 of the units lockout relay 2!, conductor 3|, armature 32 and front contact of the tens lockout relay It, to the positive pole of battery. As soon as the allotter relay 21 operates, it closes an energizing circuit for th relay 33 from the negative pole of battery, winding of this relay, upper front contact and armature of the relay 2? and thence over conductor 29 and the remainder of the circuit just described, to the positive pole of battery at the armature 32 and front contact of the relay It. When the relay 33 attracts its armatures it completes an energizing circuit from the negative pole of battery, units finder relay 54, conductor 35, front contact and armature 35 of the relay 33, outermost armature and front contact of units lockout relay 2|, to the positive pole of battery. Relay 34 is energized in this circuit. Similarly, the #2 tens finder relay 3'! is energized in a circuit traceable from the negative pole of battery, winding of this relay, conductor 58, front contact and armature 35 of relay 53, conductor 45, armature 4| and front contact of tens lockout relay It to the positive pole of battery. When the finder relays 54 and 3'! are thus operated, the tip ring and sleeve conductors respectively designated 42, 43 and 45 are extended thru the armatures of the finder relay 31, conductors 45, 45 and 47, thence thru the armature and front contacts of the units finder relay 34 to the tip, ring and sleeve conductors 45, 45 and 55 of the selected link circuit. These tip and ring conductors 48 and 49 are thus connected in series with the calling line and thru the armatures and back contacts of the relay 5|, the continuity springs and back contacts of the relay 52, thru the upper and lower windings in series of the battery feed and impulse relay 53, to the positive pole and the negative pole of battery, respectively. The impulse relay 53 is thus energized and completes a circuit from the negative pole of battery, winding of the slow release relay 54, front contact and armature of relay 53, uppermost back contact and armature of the relay 5|, to the positive pole of battery. As soon as the slow releasing relay 54 is operated, it completes a locking circuit for the tens finder relay 3'! and the units finder relay 34. This locking circuit is completed from the positive pole of battery, back contact and continuity spring of the relay 55, conductor 55, middle armature and front contact of relay 54, conductor 5", armature and front contact and winding of units finder relay 34 to the negative pole of battery and in multiple therewith thru the armature, front contact and winding of the tens finder relay 3'! to the negative pole of battery. Also when the slow releasing relay 54 is operated, it closes an energizing circuit for the slow releasing relay 58 from the negative pole of battery, winding of this relay, lowermost armature and front contact of relay 54, to the positive pole of battery. Also as soon as the slow releasing relay 54 is energized, it applies busy potential to the sleeve conductor 50 of the link. This busy potential is applied from the positive pole of battery, back contact and continuity spring of the relay 59, middle armature and front contact of the relay 54, to the sleeve conductor 55 of the link. It will be understood that this busy potential prevents the calling line from being seized by any other line.

When the slow releasing relay 58 operates, it applies positive potential at its upper armatures and front contacts to the holding conductor 60 and thence thru a branch 52 of this conductor, back contact and continuity spring of the relay 5|, conductor 63, lower Winding of the allotter relay 28 to the negative pole of battery. The allotter relay 28 on operation closes a locking circuit for itself from the negative pole of battery, front contact and upper winding of this relay, conductor 64, back contact and armature of the relay 55, associated with the last allotter relay of the series, to the positive pole of battery. It will be appreciated that as a result of this last-described circuit, the allotter relay 28 of link #1 and similar allotter relays of the remaining links of the series will operate and remain locked until the last allotter relay of the series, namely relay 280 is energized, at which time the previously lockedallotter relays of the series will release. This arrangement insures that the links ar used in rotation.

Further, when the slow releasing relay 58 operates, it applies a dialing tone, from the dial tone source, front contact and armature of relay 58, conductor 55, inner back contact and armature of relay 51, conductor 68, lower winding of the battery feed relay 52, to the negative pole of battery. Dial tone current in this circuit is repeated over the link circuit in use and over the calling subscribers line where it is heard as a dial tone in the receiver of the calling subscriber. This dial tone indicates to the calling subscriber that the apparatus is in readiness to receive the several series of code impulses corresponding to the called subscribers substation.

It has been assumed that the designation of the called subscribers substation is #214, therefore the calling subscriber operates his dial sender to transmit two impulses corresponding to the hundreds digit of this line. In response to the first impulse, the impulse relay 53 will retract its armature momentarily. This completes a circuit from the positive pole of battery, uppermost armature and back contact of relay 5|, armature and back contact of impulse relay 53, upper armature and front contact of slow releasing relay 54, conductor 59, armatures and back contacts of the busy relay It and the cut-in relay Tl conductor 72, winding of the slow releasing change-over relay l3 to the negative pole of battery. It will be understood that the changeover relay as well as the slow-releasing relay 54, fall to respond to the momentary operations of the impulse relay 53. When, however, at the conclusion of each series of impulses, the impulse relay is held operated for a considerable period of time, slow releasing change-over relay is will release. A second circuit in multiple with the energizing circuit of the change-over relay 13 is completed from the negative pole of battery, upper winding of the relay i4, uppermost back contact and armature of the relay l5, conductor I6 and thence over conductor 12 and the remainder of the circuit just described, to the positive pole of battery at the back contact and the armature of relay Thus when the impulse relay 53 retracts its armature in response to the first impulse of the hundreds digit, the changeover relay I3 and the relay 14 are both energized. With the relay 14 energized, it closes a second circuit for itself which incidentally is ineffective at this time. This second circuit extends from the negative pole of battery, upper Winding of the relay 14, its upper armature and front contact, lower winding of the relay 15, innermost lower front contact and armature of relay 13, and thence over the holding conductor Gil to the positive pole of battery at the front contact and armature of the relay 58. This last described circuit is ineffective as long as the armature of the impulse relay 53 is retracted in response to 'the first impulse, since there is positive potential present on the conductor it which serves to shunt out the lower winding of the relay 15. However, when the impulse relay 53 attracts its armature at the conclusion of the first impulse, this positive potential will be removed from the conductor 75, so that the relay M will be locked operated, and the relay 15 will be energized in the circuit which was previously described as ineffective. With relays i4 and 75 both operated, the number one counting relay H is operated from the negative pole of battery, winding of this relay, thru the back contacts and armatures of counting relays i8, 88, 82, 84 and 86, conductor 3'5, middle front contact and armature of relay is, front contact and armature of relay 75, front contact and armature of change-over relay 73, holding conductor 6| to the positive pole of battery. It should be mentioned that as soon as the change-over relay 13 operates, it completes an operating circuit for the relay 88 from the negative pole of battery, resistor 89, lowermost armature and front contact of change-over relay 13, winding of the relay 88, holding conductor 6|! to the positive pole of battery. As soon as the number one counting relay is energized, it closes a locking circuit for itself from the negative pole of battery, winding of this relay, its innermost front contact and armature, innermost back contacts and armatures of relays H to 86 inclusive, conductor 9|], middle armature and front contact of relay 88 to the positive pole of battery over the holding conductor 68. When now the impulse relay 53 retracts its armature again in response to the second impulse of the hundred digit, the lower winding of the relay M is energized from the negative pole of battery, lower winding of this relay, its front contact and armature, uppermost front contact and armature of relay l5, conductors E6 and 12, back contacts and armatures of relays H and i0, conductor 69, front contact and armature of relay 54, back contact and armature of the impulse relay 53, back contact and armature of relay 5|, to the positive pole of battery. At this time both the upper and lower windings of the relay M are energized and since this relay is differentially wound, it retracts its armatures. However, the relay i5 is maintained operated until the close of the second impulse, from the negative pole of battery thru its upper winding, front contact and armature to the positive pole of battery over conductors i6 and i2 as previously described. However at the close of the second impulse with the relays M and iii deenergized and with the number one counting relay 11 operated, the

number two counting relay 18 is energized from the negative pole of battery, winding of this relay, front contact and armature SI of relay 11 back contacts and armatures of relays I4 and 15, front contact and armature of change-over relay 13, to positive potential on the holding conductor 80. The number two counting relay 18 looks itself operated from the negative pole of battery, winding of relay 18, its inner front contact and armature, innermost back contacts and armatures of relays 19 to 86 inclusive, conductor 90, middle armature and front contact of relay 88, to positive pole of battery over holding conductor 69.

At the conclusion of the hundreds series of impulses, the change-over relay l3 retracts its armatures and at its lowermost armature and continuity spring, it opens the original energizing circuit of the relay 83. However, the relay 88 is slow releasing and before it releases it completes a circuit for itself from the positive pole of battery on the holding conductor 60, winding of the relay 88, continuity spring and back contact of the change-over relay 13, front contact and armature 92 of relay B6, armatures and back contacts of the transfer relays 93, 94 and 61, conductor 95, armature 96 and front contact of the number two counting relay 18 (now energized), winding of the hundreds relay 91, to the negative pole of battery. Relay 88 as well as the relay 91 are energized in this circuit and the relay 91 closes a locking circuit for itself from the negative pole of battery, its winding, armature and front contact, conductor 98, winding of the relay 6?, conductor 99, continuity spring and back contact of relay 5|, branch 62 of the holding conductor Ell, to the positive pole of battery. The transfer relay 6'! is not energized in this circuit since it is shunted at this time by a branch circuit 98a of the conductor 98, back contact and armature of relay 61, front contact and lowermost armature of relay 38 to the holding conductor fill. The slow releasing relay 88 is shunted in a circuit from the holding conductor 6% through the winding of relay 88, back contact and continuity spring of the change-over relay 13, front contact and armature 92 of relay 88, armatures and back contacts of relays 93, 94 and 61, conductor 95, armature 96 and front contact of relay 1B, armature and front contact of relay 9?, conductors Q8 and 98a, back contact and armature of relay 61, lower front contact and armature of relay 88 and thence to positive potential over the holding conductor 60. Shortly after the completion of this shunt circuit the relay 8% releases and at its lower armature and front contact it removes the previously described shunt circuit about the relay 6T. Relay 6? then attracts its armatures. The apparatus is now in condition to receive the impulses corresponding to the tens digit which in the present instance is assumed to be one.

In response to the single impulse of the tens series, the impulse relay 53 retracts its arma ture. When this takes place, the relay 14 is energized from the negative pole of battery, its winding, back contact and armature of the relay I5, conductors 16 and 12, back contacts and armatures of relays 1| and 10, conductor 69, front contact and armature of the relay 54, back contact and armature of the impulse relay 53, to the positive pole of battery at the back contact and armature of the relay 5|. The changeover relay 13 is also energized in multiple with the last-mentioned circuit, as previously described. As soon as the change-over relay operates, it closes an energizing circuit from the negative pole of battery, resistor 89, armature and front contact of the change-over relay l3, winding of the relay 88 to ground over the holding conductor Bil. As soon as the relay T4 is energized in the manner described, it closes a circuit thru its upper winding, its armature and front contact, lower winding of the relay I5, front contact and armature of change-over relay 13 to ground over the holding conductor 66. This last-mentioned circuit is ineffective, since it is shunted by the original energizing circuit of relay l i, which circuit includes the conductor 16, as long as the impulse relay 53 retracts its armature in response to the single tens impulse. However, at the close of this impulse, impulse relay 53 attracts its armature and opens this shunt circuit, whereupon the mentioned circuit of relays 14 and 75, which had previously been ineffective, now holds the relay M operated and operates the relay '55. With relays i i and t 0-perated, an energizing circuit is closed for the number one counting relay ll extending from the negative pole of battery, winding of this relay, back contacts and armatures of relays T8, 80, 82, 84, and 86, conductor Bl, front contacts and armatures of relays M and 15, front contact and armature of the change-over relay 73 to the positive pole of battery over the holding conductcr $8. It will be understood that the change-over relay, which is slow releasing, remains energized for a short interval but soon retracts its armatures after its energizing circuit is interrupted at the armature and back contact of the impulse relay 53, when this last-named relay attracts its armature at the conclusion of the tens series of impulses. The number one counting relay ll when operated, closes a locking circuit for itself from the negative pole of battery, its winding, front contact and armature, back contacts and armatures of relays 18 to 86 inclusive, conductor 90, armature and front contact of relay $38, to the positive pole of battery over the holding conductor 60. It will be recalled that the relay 9'! was operated and locked operated in response to the hundreds impulses. Now with the number one counting relay 1! operated and locked operated in response to the tens series of impulses, a circuit is completed for operating the tens relay Hit! of the relay connector associated with the link in use. The relay !90 is energized in a circuit traceable from the negative pole of battery, winding of this relay, conductor liii, front contact and armature m2 of the counting relay ll, conductor I03, front contact and armature E94 of the relay 9?, conductor #85, uppermost front contact and armature of relay iii, back contacts and armatures of relays 94 and Q3, armature 92 and contact of relay 88, continuity spring and back contact of change-over relay [3, winding of the relay 88 to the positive pole of battery over the holding conductor 68. The tens connector relay I00, when operated, closes a locking circuit for itself from the negative pole of battery, winding of this relay, its front contact and armature, conductor E95, winding of the relay 94, to the positive pole of battery over the holding conductor 60. The relay use is locked operated in its circuit but the relay 94 does not operate at this time since it is shunted by a circuit extending from conductor I06 thence over conductor I01, inner back contact and armature of relay 94, front contact and armature of relay 61, front contact and armature of relay 88, conductor 60 to the positive pole of battery. It will be understood that this shunt circuit is effective as long as the relay 88 is operated. However, the slow releasing relay 88 is shunted at this time and shortly afterwards retracts its armatures. This shunt circuit may be traced from the positive pole of battery connected to the conductor 60, winding of the relay 88, back contact and continuity spring of the change-over relay 13, front contact and armature 92 of relay 88, armatures and back contacts of relays 93 and 94, armature and front contact of relay 6! to conductor I05, armature H34 and front contact of relay 97, conductor i 33, armature and front contact of relay Tl, conductor IGI, front contact and armature of relay H30, conductor Hi6, winding of relay 94 and again to the positive potential connected to the holding conductor 60. A short interval after the relay 88 is thus short circuited it retracts its armatures and at its lower armature and front contact interrupts the shunt circuit that had previously existed about the winding of the switching relay 94. The switching relay 94 is now operated and attracts its armatures. Also as soon as the relay 88 deenergizes it opens the locking circuit including the conductor which has been holding the counting relay 1'! operated, thus this relay deenergizes and the apparatus is in condition to receive the impulses corresponding to the units digit of the wanted numher.

It has been assumed that the units digit of the wanted number is 4 and therefore the calling subscriber operates his dial sender to transmit four impulses. In response to each of these impulses, the impulse relay 53 retracts its armature. On the first retraction of the armature of the impulse relay, the change-over relay (3 as well as the relay M are energized as previously described. When the change-over relay is thus operated it closes a circuit for again energizing the slow releasing relay 88. Also when the relay 14 is operated, it closes an ineffective circuit as before described thru the upper winding of relay [4, its armature and front contact, lower winding of relay 15, front contact and armature of relay F3 to positive potential over the holding conductor 59. Now, when the impulse relay 53 attracts its armature at the close of the first impulse, relay l' i will remain energized and relay 3'5 will be operated. Therefore, the number one counting relay 7? will be operated as before described from the ne ative pole of battery, winding of this relay, back contacts and armatures of relay 78, 8G, 82, 84 and 86, conductor 81, front contacts and armatures of relays 14 and 15, front contact and armature of the change-over relay 1-5" to the positive pole of battery over the holdconductor 60. Relay 11, when operated, closes a locking circuit for itself thru its innermost front contact and armature and thence thru the back contacts and armatures of remaining counting relays, conductor 90, armature and front contact of relay 88; to the positive pole of battery over the holding conductor 60. In response to the second impulse of the units series, the lower winding of the relay 14 will be energized from the negative pole of battery, inner front contact and armature of the relay M, upper front contact and armature of the relay 15, conductors 18 and 1 2 to the positive pole of battery thru the back contact and-armature of the relay 53. It will be noted that the relay [4 is differentially wound and thus when both of its windings are energized, it will retract its armatures. At the upper armature and front contact of this relay, the energizing circuit thru the lower winding of the relay 15 is interrupted but relay 15 is now held operated through its upper winding, front contact and armature over conductor 16. When the impulse relay 53 attracts its armature at the close of the second impulse of the units series, the locking circuit thru the upper winding, front contact and armature of the relay 15 is interrupted so that the relay l also retracts its armatures. When this takes place the number two counting relay is energized from the negative pole of battery, winding of this relay, front contact and armature 9| of relay i1, back contacts and armatures of relays M and I5, front contact and armature of change-over relay 13 to positive pole of battery over the holding conductor 60. In response to the third impulse of the units series, relays M and 15 are operated as previously described, after which the number three counting relay i9 is energized from the negative pole of battery, winding of this relay, front contact and armature of relay 18, back contact and armatures of relays 80, 82, 84 and 86, conductor 81, frontcontacts and armatures of relays M and i5, front contact and armature of relay i3, conductor 60 to the positive pole of battery. Relay 19 onvoperation closes a locking circuit for itself thru its front contact and armature, backv contacts and armatures of relays 80 to 86 inclusive, conductor 96, armature and front contact of relay 88 to the positive pole of battery over the holding conductor 60. In response to the fourth impulse of the units series, the relay 14 will retract its armatures and when the impulse relay 53 attracts its armature at the conclusion of the fourth impulse, the relay 15 will also retract its armature. Thereupon the number four counting relay 81B is operated from the negative pole of battery, winding of this relay, front contact and armature of relay 19, back contacts and armatures of relays M and 75, front contact and armature of change-over relay 13 to the positive pole of battery on the holding conductor 60. Relay 8!) when operated, closes a looking circuit for itself through its own front contact and armature and thru the back contacts and armatures of the remaining counting relays of the series, conductor 90 to the positive pole of battery on holding conductor 69 through the armature and front contact of relay 88, as previously described. 7

At the close of the units series of impulses when the impulse relay 53 holds its armature attracted, the change-over relay l3 deenergizes. Thereupon the units connector relay N38 is operated from the negative pole of battery, winding of this relay, conductor 159, front contact and armature Hi3 of the number four counting relay B6, conductor ill, uppermost front contact and armature of relay J l, back contact and armature of relay $3, armature 92 and front contact of relay 88, back contact and continuity spring of chan e-over relay 73, winding of the slow releasing relay 88 to positive pole of battery over the holding conductor Eli. The connector relay le on operating, closes a locking circuit for itself from negative pole of battery, winding of this relay, its front contact and armature, conductor H2, winding of the relay 93, to the positive pole of battery over the conductor 56. The relay 33 is not operated at this time, since it is shunted by a circuit includingconductor H2, conductor H3, back contact and armature cuit.

of the relay 93, front contacts and armatures of relays 94 and 61, front contact and armature of relay 88, to the holding conductor 60. However, the slow releasing relay 88 is also shortcircuited by the operation of the units connector, relay I08 and shortly afterwards retracts its armature so that the relay 93 will be operated. The mentioned short circuit for the relay 88 extends from the holding conductor 60, winding of the relay 88, back contact and continuity spring of the change-over relay I3, front contact and armature 92 of relay 88, back contact and armature of relay 9-3, armature and front contact of relay fi l, conductor l I l, armature H0 and front contact of the counting relay 80, conductor 109, front contact and armature of relay l 08, conductor I l2, winding of relay 93 and again to the holding conductor 66. Relay 88 thereupon releases and by so doing, removes the short circuit about the relay 93, which then operates.

Since the connector relays Hill and H18 have been operated, the link circuit in use is connected to the tip ring and sleeve conductors of the called subscribers line. The testing of this line now takes place. If this line is idle, positive potential will be absent from its sleeve conductor H4 and therefore the busy test relay 10 will not operate. Consequently, no busy tone will be transmitted to the calling subscriber and he will therefore know that he can now operate his dial sender to transmit impulses for selecting the proper ringing frequency to signal the desired calling substation on the telephone line to which his substation has been connected. It will be noted in the present arrangement, that provision is made for selectively signalling anyone of ten substations on a called telephone line. purpose five different ringing frequencies namely sixteen, thirty, forty-two, fifty-four and sixty-six cycle ringing current are provided. Let it be assumed that sixty-six cycle ringing current will signal the wanted substation. Therefore the calling subscriber operates his dial sender to transmit a series of five impulses to select that frequency. In response to the first impulse the changeover relay i3 is operated and remains operated during the series of impulses. Also in response to the five mentioned impulses, the counting relays for numbers 1 to 5 inclusive, designated TI to 8|, inclusive, are first energized and then deenergized when the succeeding relay in the series operates. Consequently. only the #5 counting relay 8! remainsoperated. As soon as the change-over relay [3 is operated, it closes an energizing circuit for the relay 838 which circuit extends from the negative pole of battery, resistor 89, armature and front contact of change-over relay T3, winding of the relay 88 to the positive pole of battery over the holding conductor 60. 93 is operated as previously described, a circuit is closed for the ringing relay l l 5 from the negative pole of battery, resistor HE, winding of the relay I I5, back contact and armature of the cutin relay H, front contacts and armatures of relays 93, 94 and 61, front contact and armature of relay 83, to the positive pole of battery over the holding conductor Bil. The ringing relay H5 when operated, closes a locking circuit for itself thru its innermost front contact and armature over the holding conductor 59 to the positive pole of battery. The ringing relay H5 when operated also closes at its uppermost armatures and front contacts break points in the link cir- After the change-over relay releases but For this When the transfer relay before the slow releasing relay 88 deenergizes, a circuit is completed for operating the cut-in relay H. This circuit is traceable from the negative pole of battery, lower winding of this relay, back contact and armature H? of the relay H8, conductor IE9, front contact and armature of relay 83, armature 92 and front contact of relay 88, back contact and continuity spring of change-over relay I3, winding of relay 88 over the holding conductor 60 to the positive pole of battery. With the cut-in relay II operated, a second pair of break points is closed in the link circuit. Since the counting relay 8| has been operated, 66 cycle ringing current is applied thru the front contact and armature I20 of relay 8|, back contacts and armatures of relays 89, I3, 18 and T2, winding of the trip relay I2I, back contact and armature of the reversing relay I22, conductor I23, front contacts and armatures of the ringing relay H and cut-in relay II, tip conductor I24 of the link and thence over the tip conductor of the called telephone line, thru the substation ringer of the wanted substation, ring conductor of the called telephone line, ring conductor I25 of the link, front contacts and armatures of the cut-in relay II, ringing relay H5, conductor I26, armature and back contact of relay I22. to the generator return. It should be pointed out that the operation of the cut-in relay II and the ringing relay H5, closes a circuit thru their front contacts and armatures I21 and I28 for starting the ringing generator. It should be noted that in the present instance, the reversing relay I22 was not operated since the number of impulses in the ringing series of impulses was less than six. If however, the number of impulses in the ringing series was six or more, the reversing relay I22 would have been operated so that the ringing current would have been applied to the ring side of the line. This enables the ten difierent substations on a telephone line to be selectively signalled with the use of only five different cycles of ringing frequency, five connected between the tip line to ground and five connected from the ring side to ground. It will be appreciated that when the number of impulses in the ringing series is six or more, the reversing relay I22 will be operated from the negative pole of battery, its winding, continuity spring and back contact, front contact and armature of the transfer relay 93, armature and front contact of relay '88, conductor I29, front contact and armature I 3!! of the number five counting relay 8|, back contacts and armatures of relays M and I5, inner front contact and armature of the change-over relay I3 and thence to the positive pole of battery over the holding conductor 89. Thus when any of the counting relays 82 to 86 inclusive ar selected, the proper one of the five different cycles of ringing frequency will be selected, but in this instance the selected frequency will be applied to the ring side of the called telephone line.

When the subscriber at the called station responds by removing his receiver from its switchhook, the marginal trip relay i2I will be operated. At the armature and front contact of the trip relay, a shunt circuit is completed about the ringing relay H5 which deenergizes to close one pair of break points in the called end of the link circuit. The telephone connection is now completed, the talking battery being supplied to the calling party thru the windings of the impulse relay 53 and the talking battery being supplied to the called substation thru the windings of the relay 52.

At the conclusion of the conversation when the calling subscriber replaces his receiver on its switchhook, th impulse relay 53 will release. Shortly afterwards, the slow releasing relay 54 deenergizes and opens the circuit which has been holding the finder relays operated. Shortly after the release of relay 54, the slow releasing relay 58 deenergizes. When this relay releases, it removes positive potential from the holding conductor 60 so that all of the operated relays of the link circuit will be restored to normal.

Let it be assumed that the called telephone line was busy at the time when it was tested. Under this condition the busy relay #0 is energized from the negative pole of battery, winding of this relay, back contact and armature of the relay 93, sleeve conductor I M to the positive pole of battery which is maintaining the called telephone line busy. Relay 'Iil when operated, locks itself operated thru innermost lower armature and front contact over the holding conductor 6t. Also prior to the energization of the transfer relay 93, the relay H8 will be operated from the negative pole of battery, winding of this relay, armature and front contact of the busy relay I8, back contact and continuity spring of relay 93, to the positive pole of battery over the holding conductor 60. Relay I I8 will be released when relay 93 opens the above described operating circuit. This is because the locking circuit for relay I is is open at the lower back contact of relay 59. The operation of relay 59 will be described later.

Provision is made for releasing a link circuit in the event that a called subscriber on a revertive call does not answer or in the event that the calling subscriber does not hang up when the called subscriber replaces his receiver on the switchhook, which would otherwise hold the link circuit if the calling subscriber maliciously failed to hang up at the conclusion of the call with the intent of tying up the called subscribers line. A timing circuit arrangement for effecting this result is shown at the bottom of Fig. 3 and at the lefthand portion of Fig. 7. In this timing arrangement, when the relay 52 (Fig. 7) is deenergized and the relay 58 energized, the timing relay is energized in a circuit traceable from the negative pole of battery, winding of relay 23I (lower part of Fig. 3), conductor 232, armature and back contact of relay 52, front contact and armature 233 of relay 58, winding of slow releasing relay 55, its continuity spring and back contact, conductor 234, armature and back contact of relay 235, armature and back contact of slow releasing relay 236, back contact and armature of slow releasing relay 231 to the positive pole of battery. Relay 55 when thus operated, locks itself operated in series with the relay 23I over the conductor 232, winding of relay 55, its lower front contacts and armatures, conductor 238, back contact and armature 236 to the positive pole of battery. As soon as the relay 23I is energized, it closes an obvious energizing circuit for the slow releasing relay 233 and this relay at its armature and front contact, closes a circuit for the motor (not shown) which alternately opens and closes the contacts 259. These contacts are arranged to be closed for 2 minutes and opened for 2 seconds. As soon as contacts 240 are closed, an obvious circuit is completed for the relay 235. This relay at its lower armature and front contact completes a multiple circuit which maintains the slow releasing relay 239 operated so that the motor will continue to run. Also when the relay 23I operates, it completes a circuit for operating the slow-releasing relay 231 from the negative pole of battery, winding of this relay, middle front contact and armature of relay 23!, front contact and armature of relay 235 to the positive pole of battery. Relay 231 then locks itself operated thru the inner front contact and armature of relay 23i When the relay 235 deenergizes at the close of a 2 minute interval the relay 236 is energized in a circuit traceable from a negative pole of battery, winding of this relay, front contact and armature of relay 231, back contact and armature of relay 235 to the positive pole of battery. When the relay 236 operates, it opens at its uppermost armature and back contact a looking circuit which has been maintaining the relay 55 operated. The relay 55 then deenergizes to effect the release of the link. The deenergization of this looking circuit also removes positive battery from conductor 51't0 effect the release of the tens and units finder relays of Fig. 2 for disconnecting the calling line from the link. This effects the release of cut-01f relay H, after which line relay in is operated by the closed circuit of the calling line. Relay l closes a circuit for locking relay I8, before this latter relay is released by its deenergization when relay I! was released. With relays l0 and I 8 energized, the circuit to the common lock-out relays is maintained open, thus preventing the seizure of a link until the calling party disconnects and again initiates a call.

Revertivc call In the event that the called line is found busy at the time of the busy test, due to the fact that the calling line and the called line are one and the same, in other words, a revertive call, provision is made in the present system for handling such a call. It will be remembered that at the time the busy test is made, the busy test relay i6 is operated and thru its innermost, lower front contact and armature, it closes a locking circuit for itself over the locking conductor 50. It will further be remembered that this test of the busy line is eifected before the transfer relay 93 (Fig. 9) is energized. During this interval the relay H8 will be operated from the negative pole of battery, winding of relay H8, front contact of relay Ill, conductor 220, back contact and continuity spring of relay 9.3, branch conductor 22! and the holding conductor 60 to the positive pole of battery. The operation of relay H8 at its armature 222 and back contact, interrupts the circuit thru the upper wind-- ing of relay 59 which has previously maintained this relay energized. With the armature 2'22 and the front contact of relay H8 closed, a circuit is completed from the positive pole of battery, holding conductor 60, armature 222 and front contact of relay 1 I8, branch conductor 223, sleeve conductor H4 of the link which is now connected to the sleeve conductor of the called line thru the operation of the connector relays. Since the sleeve conductor H4 is connected to the sleeve conductor of the called line, it will also be connected to the sleeve conductor of the calling line inasmuch as they are branches of the same conductor, thence thru the sleeve conductor which is extended by the finder relays to the sleeve conductor 50 of the link in use, armature 224 and front contact of relay 54, continuity spring and armature of relay 59, lower winding of this relay to the positive pole of with the link in use is restored.

battery. Thus the lower winding of the relay 59 is included in a shunt circuit and since the circuit thru its upper winding has been interrupted, this relay releases. When now the transfer relay 93 is operated as previously described, the relay H8 will have a locking circuit completed for itself from the negative pole of battery, winding of this relay, lowermost back contact and armature of relay 59, front contact and armature of relay H8, conductor 225, front contact and continuity spring of relay 93, branch conductor 22| and holding conductor 60 to the positive pole of battery. It will be noted that at the time of the operation of the relay H8, the normal energizing circuit for the cut-in relay i! is interrupted at the back contact and armature ll! of the relay H8. Thus ringing current is not applied to the called line at this time. However, the calling subscriber who is making a revertive call is instructed in the directions of his telephone directory or otherwise, that when he receives a busy signal on the occasion of calling a subscriber on his own line, he shall replace his receiver on its switchhook for an interval long enough to permit signalling current to be applied to the called line to signal the called subscriber. Thus when the calling subscriber hangs up, the impulse relay 53 will be deenergized and shortly thereafter the slow releasing relay 54 will release. The release of the relay 54 interrupts the holding conductor 51 which has maintained the finder switching relays of the link operated, so that these relays are restored but the calling line connection to the link in use is not interrupted since it is now by way of the connector relays. When the slow releasing relay 54 releases, a circuit is completed for the upper winding of the cut-in relay H. This circuit is traceable from the positive pole of battery, armature 226 and front contact of relay H8, upper winding of the relay H, continuity spring and back contact of the relay 52', lowermost back contact and armature of relay 5d. winding-of the slow releasing relay 58, to the negative pole of battery. Thus when the relay 54 releases, the cut-in relay TI is operated and the slow releasing relay 53 is continued operated to maintain, at its upper armatures and front contacts, positive potential on the holding conductor 56. With the cut-in relay H operated break points are closed in the link conductor I24 and so that the selected ringing current is applied over this end of the link to the called subscribers line. When the calling or called party responds, the trip relay i2! is energized as previously described and completes a circuit including the conductor 99 which shunts the ringing relay H5. The release of the relay H5 closes another pair of break points in the link conductors E24 and l25 and at the same time disconnects ringing current from the link circuit. On the response of the called subscriber, the re lay 52 (Fig. '7) is energized and its continuity spring and back contact interrupts the circuit which has been maintaining the cut-in relay H and the slow releasing relay 58 energized. When the relay 5% releases, it interrupts at its upper mest armatures and front contacts the holding conductor 55 so that the apparatus associated Thus the common equipment employed thus far in the connection including the finder relays of the link as well as the link and the connector relays are restored to normal. On the release of the link from this connection, the cutoff relay H of the calling subscriber (Fig. 6), which is also common to the line of the called subscriber, deenergizes and talking battery is then supplied for this revertive call line thru the windings of the line relay Ill. It should be noted that after the link circuit is released as above set forth, a second link circuit is not connected to the calling line. It ill be seen that while the cutoff relay II is energized, the slow releasing relay I8 is operated from the negative pole of battery, winding of this relay, front contact and armature of cut oif relay l I to the positive pole of battery. When however, the cut-off relay II is released in the manner just described, the line relay I will again be operated thru the called subscribers substation. With the line relay Ill operated the slow releasing relay I3 is maintained operated from the negative pole of battery, winding of this relay, its innermost front contact and armature, front contact and armature of line relay I8; middle armature and front contact of slow releasing relay it, winding of the relay 230 to the positive pole of battery. Relay 235 closes a lamp circuit indicating that a revertive call is in process so that in the event that the lamp circuit is lighted for an abnormal period, an attendant can investigate to find out whether or not the system is functioning properly. It will be recalled that the inner and middle armatures and back contacts of relay I8, controls the lockout circuit which includes the tens relay I6 and the units relay 21. These relays when operated control the association of a link circuit with the calling line and since this lockout circuit is interrupted during a revertive call, no link circuit is associated with this line.

On the conclusion of this revertive call when both subscribers replace their receivers, the line relay Iii will deenergize and the equipment that has been used in this call will all be restored to normal in readiness for a succeeding call.

Call from dial office to distant manual ojfice Referring to Fig. 3, when the connector relays of a link in use, select a two-way trunk circuit, a circuit is closed from the calling line and this link across the conductors I50 and I5I to operate the relay I52. This relay closes an obvious circuit for operating the relay I53. Relay I53 completes a circuit for operating the relay I54 from the negative pole of battery, winding of this relay, conductor I55, front contact and armature of relay I53 to the positive pole of battery Relay I53 on operation also applies positive battery to the allotter conductor I51 for making this trunk busy and also applies positive battery to the sleeve conductor I58 of the trunk for operating relay 5I (Fig. 8), of the link. Furthermore, the operation of relay I53 at its upper armature and back contact opens the circuit of the normally energizing ringing relay lEI, to permit this slow releasing relay to deenergize but not until the slow releasing relay I5! is operated. The joint action of relays I54 and Isl applies an impulse of ringing current to the primary windings of the repeating coil. I52 for the purpose of applying a short impulse or" ringing current over the two sides of the trunk leading to the distant manual oflice. This impulse of alternating current is effective to operate the alternating current relay I63 (Fig. 4) which closes a circuit for operating the relay I64. This circuit is traceable from the negative pole of battery, winding of the slow releasing relay I64, back contact and armature I65 of relay I68, back contact and armature Itl of relay I68, conductor IE9, armature and front contact of relay I53, back contact and continuity spring of relay I54 to the positive pole of battery. Relay IM on operating closes a locking circuit for itself independent of the control of the alternating current relay I53. This circuit extends from the negative pole of battery, winding of relay IM, back contact and armature I10 of relay S66, armature and continuity spring of relay I54 to the positive pole of battery. Relay Iii-'1 when operated, closes a circuit at its front contact and armature I12 for lighting the incoming or line lamp I13 which indicates to the manual operator at the distant manual office that a call is awaiting extension on this trunk, At the close of the impulse of alternating current, the alternating current relay I53 releases but the slow releasing relay I64 has been operated and looked as previously described. When the operator answers by inserting an answering plug P into the jack J of the trunk on which the call is waiting extension, relay I66 is energized in a circuit from the negative pole of battery, winding of this relay, uppermost contact and armature of relay 68, back contact and armature I14 of relay I64, conductor I15, jack contacts I16 (now closed), to the positive pole of battery. Relay 566 when operated, closes a locking circuit for itself from the negative pole of battery, its winding, uppermost back contact and armature of relay I68, innermost contact and armature of relay I 66, to the positive pole of battery over conductor i15 as previously described. The operation of relay I65 opens the locking circuit for the slow releasing relay I64, which circuit is now interrupted at the back contact and armature I1il of relay I53. Since the relay I64 is slow releasing, there will be a short interval during which an impulse of alternating current is transmitted back to the trunk to operate al ternating current relay I86 (Fig. 3). This is effected by the operation of the relay I11 which is energized in a circuit closed from the negative pole of battery, winding of this relay, armature and front contact of the ringing relay I18, conductor I19, front contact and armature I10 of relay I86, armature and front contact of relay I64 to the positive pole of battery. When after a short interval the slow releasing relay I64 releases, it interrupts the circuit just described and relay I11 releases. Also the release of the relay I54 opens the previously described circuit for the line lamp I155 which is thus extinguished. On the insertion of the plug P into the jack J, the relay I is energized from the positive pole of battery, winding of the marginal relay I8I, winding of the relay I 38, conductor I82, sleeve contacts of the jack and plug, conductor I83, through the coil I84 and resistor I85 in multiple, to the negative pole of battery. However, the operation of the relay I88 at this time performs no function on this class of call, since the marginal relay I85 does not operate in series with the resistance of the coil I84 and the resistor I85,

The operation of the alternating current relay I85 in response to the impulse of alternating current transmitted back over the trunk in the manner just described, effects the operation of the slow releasing relay 81 in an obvious circuit. The energization of relay l5? completes an energizing circuit for the relay 53% in multiple with the slow releasing relay I5 1. This circuit extends from the negative pole of battery, Winding of the relay I89, front contact and armature of relay I81, conductor I55, armature and front contact of relay I53, to the positive pole of battery.

At the termination of this impulse of alternating current, the relays I86, I 81 and I89 release in sequence. When the relay I81 releases, the relay I90 is operated in a circuit from the negative pole of battery, winding of this relay, inner front contact and armature of relay I89, back contact and armature of relay I81, conductor I55, front contact and armature of relay I53 to the positive pole of battery. Relay I90 when thus operated, closes a locking circuit for itself through its lower front contact and armature, back contact and armature of relay I81 and thence to the positive pole of battery as previously described. Thus the relay I90 remains energized after the relay I89 deenergizes.

The manual operator is now connected to the calling party and after obtaining the number of the wanted party extends the connection" to the wanted line in the usual manner by signalling the subscriber thereon (by means not shown), after which conversation takes place.

At the conclusion of the conversation when the calling subscriber hangs up, the relays I52, I53 and I54 release in sequence. The release of relay I53 opens the circuit including the sleeve conductor I58 of the link circuit in use which operation is effective to release the cut off relay II of the calling line, as well as the relay of the link. The release of relay 5I efiects the release of the tens and units finder relays. As soon as the relay I53 deenergizes, it closes a circuit for again operating the ringing relay I6I. As soon as this ringing relay operates and before the switching relay I54 releases, an impulse of alternating current is transmitted forward over the trunk as a disconnect signal. This impulse of alternating current causes the. relay I63 (Fig. 4) to operate and release. The operation of the relay I63 completes an operating circuit for the relay I9I extending from the negative pole of battery at the common coin box tone key I92, lower winding of relay I9I, front contact and armature I65 of relay I66, back contact and armature I61 of relay I68, armature and front contact of relay I63, back contact and continuity spring of relay I64 to the positive pole of battery. Relay I9I on operation closes a locking circuit for itself from the negative pole of battery through its upper winding, its inner front contact and armature, conductor I92, armature I93 and front contact of relay I66, back contact and armature of relay I66, back contact and armature I14 of relay I64, conductor I15, jack contacts I16, to the positivepole of battery. The operation of the relay I9I includes condensers I94 and I95 in the conductors leading to the repeating coil circuit which is efiective to release the supervisory relay (not shown) of the cord circuit at the manual ofiice, for giving the operator disconnect supervision. When the operator disconnects by removing the plug P from the jack J, relays I66, ISI and I 80 release. The busy lamp I95 continues to be lighted as long as this trunk is in use, since its circuit is closed. when the operator answers but is opened by the release of relay I66 when the operator disconnects.

Call from the manual ofiice to the dial ojfice On the initiation of a call from the manual ofiice to the dial office, the operator inserts a calling plug similar to P into the jack J. This causes the relay I60 to be energized in series with the marginal relay I8I as previously described. However, the marginal'relay I8I does not operate at this time. The relay I68 (Fig. 4) is next energized from the negative pole of battery, Winding of this relay, back contact and armature ofrelay I66, back contact and armature I14 of relay I64, conductor I15, jack contacts I16 to the positive pole of battery. The operation of relay I68 causes the slow-operate and slow-release ringing relay I18 to release and in the interval before the relay I18 releases, the relay I11 is operated from the negative poleof battery, Winding of this relay, conductor 200, armature and front contact of relay I18, front contact and armature of relay I58 to the positive pole of battery. With the relay- I11 operated, at its front contacts and armatures, it applies generator current to the-trunk for operating the relay 201 through the rectifying bridge network RB (Fig. 3). Relay 20 I completes a circuit for operating the relay 202 in a circuit from the negative pole of battery, winding of this relay, inner front contact and armature of relay 20I to the positive pole of battery. In addition, the relay 20I applies positive potential to the allotter conductor I51 which makes the calling end of the trunk busy. Relay 202 completes a circuit for operating the slow releasing relay 203 which circuit is traceable from the negative pole of battery, winding of this relay, back contact and armature of slow releasing relay 204, front contact and armature of relay 202 to the positive pole of battery. Relay 203 on operating, closes a break point in a locking circuit for itself thru its lower innermost frontcontact and armature, back contact and armature of relay 202 (when this relay releases) to the positive pole of battery. On the operation of the relay 203, the slow releasing relay 204 isoperated in a circuit extending from the negative pole 'of battery, front contact and armature of relay 203, front contact and armature of relay 202 to the positive pole of battery. Relay 204 locks itself operated at the armature and front contact of relay 202. When the impulse of alternating current terminates, relays 20I and 202 deenergize. Relay 202 on releasing, closes the previously 'mentioned locking circuit for the relay 203. Relay 204 now has its energizing circuit interrupted at the lowermost front contact and armature of relay 202. With the relay 202 deenergized and with relay 203 operated, a circuit is closed across the tip 'and ring conductors of the incoming line circuit. This .causes an idle link circuit to connect with the line circuit now in use. When this connection is effected the operator can then proceed to dial the required number. With the dial cit-normal contacts 205 (Fig. 4) closed, the negative pole of battery is connected thru the low resistance coil 206, off normal contacts 205 and impulse contacts 201 of the dial, conductor 208, contacts of the dial key 209, sleeve contacts of the plug P and jack J, conductor I82, winding of relay I and marginal relay I8I, to thepositive pole of battery. The marginal relay I8I is operated in this circuit. When the operator actuates the dial, the circuit last described is opened at thedial impulse springs 201 a number of times corresponding to the number dialed. At each interruption of the impulse circuit, caused by the dial operation, the relays I80 and I8I -are released and. again energized after the interruptions. At the end-of the dialing operation, the marginalrelay I8I does not energize because the dial off normal contacts 265 opens the circuit thru the low resistance coil 266 leaving a high resistance circuit including coils 284 and 285, completed thru the mentioned sleeve contacts. When the relay I8I is thus intermittently energized, it extends a circuit for the slow releasing relay 2H] from the negative pole of battery, winding of this relay, front contact and armature of relay I6I, conductor I15, jack contacts I16 to the positive pole of battery. This circuit holds the slow releasing relay 2H] operated during the series of impulses. However, the relay H is released during the interval between each series of impulses. In response to each dial impulse, the relay I11 (Fig. 4) is energized in a circuit extending from the negative pole of battery, winding of this relay, conductor armature and back contact of the ringing relay I16, conductor ZI I, lower front contact and armature of relay 2I6, back contact and armature of relay I86, conductor I15, jack contacts I16 to the positive pole of battery. Therefore, an impulse of alternating current is applied at the front contacts and armatures of relay I11 at each interruption of the impulse circuit at the dial impulse springs, which impulse of alternating current is transmitted over the trunk leading to the dial office. Since the slow releasing relay I54 (Fig. 3) is deenergized at this time, these impulses of current are applied to the rectifying bridge RB which operates to apply pulsating current corresponding to these impulses to the relay 26L It will be appreciated that these pulsations in this rectified current are sufficiently smooth to operate the relay 20I without chatter and also permit this relay to release at the end of each impulse period. Relay 20I (Fig. 3) and relay I86 (Fig. 4) therefore follow the impulses corresponding to the number designation of the wanted subscriber in the dial office. The relay 262 at its back contact controls the impulse circuit leading to the link which was selected. This supplies impulses to the link in accordance with the impulses received over the trunk circuit. When the link has been connected to the line of the wanted subscriber this line is tested for its busy or idle condition and if found idle, ringing current is applied thereto in the manner previously described. When the called subscriber answers, the polarized relay 2 (Fig. 3) is energized to close an obvious circuit for the slow releasing relay 2I2.

When the called subscriber hangs up, relays 2H and 2I2 are released in sequence. During the time interval required for the relay 2I2 torelease, a circuit is extended for operating the slow releasing switching relay I54. This circuit is completed from the negative pole of battery, winding of this relay, conductor I55, front contact and armature of slow releasing relay 2I2, back contact and armature of relay 2II to the positive pole of battery. However, when relay 2I2 releases the switching relay I54 will also release. But during the interval when relay I54 is energized, alternating current is extended thru the front contacts and armatures of relay I6I, front contacts and armatures of relay I54 to the windings of repeating coil I62 and thence by induction over the trunk to give a disconnect signal. The impulse of alternating current actuates the alternating current relay I63 (Fig. 4). Since relay I68 is energized at this time, the relay I9I is energized from the negative pole of battery, common coin box tone key I92, lower winding of relay I9I, front contact'and arma- '75 ture I61 of relay I68, armature and front contact of relay I63, back contact and continuity spring of relay I64 to the positive pole of battery. Relay I9I locks itself operated and connects the condensers I94 and I in series with the talking conductors of the cord circuit in use. This effects the release of the supervisory relay (not shown) of the cord circuit in use, for giving the operator disconnect supervision.

The release of the connection from the manual office to the dial ofiice is indicated by an extra long impulse of alternating current applied to the trunk circuit. This is accomplished by the release of the relay I68 when the operator removes the plug P from the jack J.

It will be recalled that the relay I63 has been maintained energized in a circuit extending from the negative pole of battery, winding of this relay, back contact and armature of relay I66, back contact and armature I14 of relay I64, conductor I15, jack contacts I16 to the positive pole of battery. When the operator releases the connection by removing the plug P from the jack J, contacts I16 are opened. On the release of the relay I68, the slow-to-operate ringing relay I13 is energized at the back contact and armature of relay I68, and the relay I11 is now operated from the negative pole of battery, winding of this relay, conductor 2I5, front contact and armature of slow releasing relay 2I6, back contact and armature of relay I68 to the positive pole of battery. It will be understood that when the slow to operate ringing relay I18 is energized, it opens the operating'circuit of the slow releasing relay 2I6. In this interval when relay I18 is operating and relay M6 is releasing, the relay I11 is operated as described for an extra long interval due to the delayed action of relays I18 and H6. The operation of relay I11 applies alternating current over the trunk. In response to this impulse, the rectifying bridge RB functions to operate the relay 26I. Relay 2IlI at its inner front contact and armature, completes a circuit which operates the relay 262. When relay 262 operates, it opens its lowermost armature and back contact and thereby interrupts the locking circuit of the slow releasing relay 203. At the close of the impulse of alternating current, relays ZIlI and 202 release in sequence and with the relay 202 deenergized the locking circuit of the slow releasing relay 263 is opened so that this relay deenergizes. Relay 262 was therefore energized for an extra long time interval as described for releasing the connection to the dial office by holding the line circuit open for an extra long period of time.

Coin box tone If a subscribers line equipped with a coin box selects a trunk leading to the manual office (Fig. 3), an impulse of coin box tone current is applied to this trunk when the operator answers. The operator can also apply ringing current (by means not shown) back over the trunk while operating the common coin box key'I 92 for again causing coin box tone to be momentarily applied to the trunk. In this way an indication is given to the distant operator when the calling substation is equipped with a coin box.

This coin box tone is applied to the trunk at the time that the operator answers and during the time that the relay I66 (Fig. 3) is released and the relay I81 is operated. -It will be understood that a station equipped with a tone box has a coin box tone connection made to the

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