US1257392A

US1257392A - Telephone-line-selecting system.

Info

Publication number: US1257392A
Application number: US19998317A
Authority: US
Inventors: Frank N Reeves; Alben E Lundell
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1917-11-02
Filing date: 1917-11-02
Publication date: 1918-02-26
Anticipated expiration: 1935-02-26

Description

F. N. REEVES & A. E. LUNDEL'L,

TELEPHONE L INE SELECTING SYSTEM. APPLICATION FILED APR. 16.1915. RENEWED Nov. 2. 1911.

1,257,392. Patented Feb.26,1918.

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I messes; mm/r N. Reel/es A/ben E. Lunae/l F. N. REEVES & A. E. LUNDELL TELEPHONELINE SELECTING SYSTEM.

APPLICATION FILED APR. 16, 1915- RENEWED NOV. 2. I917.

Patented Feb. 26, 1918.

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TELEPHONE LINE SELECTING SYSTEM.

APPLICATION FILED APR.,16.1915. RENEWED NOV-2.1911.

F. N. REEVES 61 A. E. LUNDELL.

TEEEPHONE LINE SELECTING SYSTEM.

APPLICATION FILED APE. 16. 1915. RENEWED N0v,2,1s12.

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F. N. REEVES & A. E. LUNDELL.-

TELEPHONE LINE SELECTING SYSTEM. APPLICATION FILED APR. 16 19 15- RENEWED NOV. 2,1917.

Patented Feb. 26, 1918 5 SHEETS-SHEET 5.

lnven/ors: Frank N Reeves A/ben E. Luna/ell I y Wimessea:

UNlTEL FRANK N. REEVES, G1 NE N. Y., ASS-IGNG 1K, NEW JERSEY, AND ALBEN E. LUNDELL, OF NEW YQBK, n.- s, BY Ad-ESNE ASSlGNMENTS, TO WESTERN ELECTRIC COMPANY.

INCORPORATED, A CORPORATION OF NEW YORK.

TELEPHGNE-LINE-SELECTING SYSTEM.

Specification of Letters Patent.

lztteiited Feb. as, lil fti.

Application filed April 18, 1815, Serial No. 21 896. Renewed November 2, 1917. Serial No. 199,983.

This invention relates to line selectors orconnectors. and particularly to means associated therewith for testing the lines. It is especially applicable to connectors of automatic and semi-automatic telephone exchange systen'ls.

It is desirable for traliic reasons in a telephone exchange system to permit certain operators, such as the operators at a toll or long distance switchboard or incoming operators to establish connections with wanted lines regardless whether they are at the mon'ient busy or idle. Thus in an automatic or semi-automatic exchange it becomes necessary. in'order to meet the traflic requirements referred to, to force connections to busy lines in some manner regardless of the testing means at the connectors which ordinarily operate to reject connections to busy lines. lt is the object of this invention to enable any connection, available through a connector switch acting under the control of a sender. to be made or to be rejected by a busy line. at the will of the operator or other person manipulating the sender, and to autou'iatically apply the busy test condi tion to an idle line when a connection thereto is established through a connector without regard to the previous test condition of the selected line.

ln accordance with one feature of the invention the incoming line. i. (A. the line extending between the sender and the connector. is ayailable not only for controlling; the selecting operation. but also for controlling the tesisn'g means thcreoi whereby. it dosircd. it may be rendered temporarily ineffective. The invention provides. furthermore. a no test controlling device or key at the sender. which may be adjusted by the operator before or during the sending operation. and which shall automatically cause a, change to occur in the testing moans after the line wanted is selected and before said testing means can become effective to reject a busy line connection. The change in the testing means referred to may be rendered eiiective at the proper time by means of a no test relay associated with the line selector, and this relay preferably is provided with a locking contact by which it isheld energized after receiving a momentary impulse of current over the incoming line. The no test relay when thus energized, or some other automatically available means, may be caused to apply the busy test conditionto the selected line so that this line, if it had happened to have been idle, will quickly bemade busy to other selectors operatcd in the ordinary way.

The invention will be more fully understood by reference to the accompanying drawings illustrative of the circuits of a semi-automatic system. Figs. 1, 2. 3 and d are to be placed adjacent one another from left to right in numerical order and Fig. 5 below Fig. 2. Fig. 1 represents a toll line and connecting apparatus'of a toll opcrators switchboard; Fig. 2, the circuits of a cordless incoming selector; Fig. 3, part of the circuits of a line selector or connector; Fig. l. diagrannnatically. certain portions of the connector structure. part of the circuit connections thereof and the circuits of the local snbscribrflslinei and Fig. 5, certain of the circuits of a sender apparatus adapted for i'nani1'iulation by an operator when associated with the cordless incoming selector of Fig. 2.

For the purpose of producing various circuit changes required at the incoming selector (Fig. 2), there is provided a sequence switch 200; having a plurality of successive resting positions, certain of which are as "Follows: 1 normal, 13final selector control. 14-awaiting trunk closure, 16- talking. 18 selector restoring. The circuits of the lineselector (Fig. 3') also are controlled by a sequence switch 300, certain of the resting positions of which are: 1norinal. 6-selector control. 7awaiting trunk closure. Stesting line. 14return on busy. i6 .tallting. l7busy-back. and ]Q-sclector restoring. And the circuits of the sender (Fig. 5) are provided with a sequence switch 500. certain of the resting positions ot which are: l-nor1nal. 13-iinal select-or ,cont-rol, 16awaiting disconnect In the complete apparatus certain other sequence switch positions than those specified may be used. For example, positions 2 to 12 inclusive of the sequence switch 200 may oe utilized for the control of the circuits during the selecting operations of the incoming and line selectors preceding the final or units operation of the latter which occurs in position 13 of the sequence switch 200, position 6 of sequence switch 300, and position '13 of sequence switch 500. As the preliminary selecting operations, however, do not have any special bearing on the invention claimed herein, and for the sake of brevity a description of the operations which take place in them and the detail circuits involved therein are omitted.

The heavy black lines running through Figs. 1 to 4 inclusive indicate the conductors through which a telephonic circuit may be established from station 100 of a toll line to station 400 of a local subscriber-s line. This connection in part includes means, such as an answering plug and jack of an automatic switch, by which the call from station 100 is extended to a connecting circuit 101 of a toll operator position, and a calling plug 102 and trunk jack 103, by which the call is extended to the circuits of a cordless incoming selector 201 (Fig. 2). The latter connection may be established in accordance with instructions given by an incoming operator to the toll operator over an order wire, as to the particular incoming trunk or selector which the former operator assigns for the connection. By- .mcans of such an order wire (commonly used and not shown in the drawings), the toll operator had previously announced to the incoming operator the number of the wanted subscribers line. When the incoming operator has assigned the trunk, she depresses an assign ment key 202 which starts into operation apparatus for t-enmorarily associating a sender apparatus (Fig. 5) to the assigned trunk. The connection between the trunk and the sender may be made through the usual cord finder 501, certain of the contact of which are shown. The connection having proceeded as stated to the cordless incoming selector 201, and, the sender of Fig. -5 havmr;- been connected to the incoming trunk, the incomingdrunl; operator proceeds to effect the operation oi the selector switches in the usual way. ihe operator may, for example, register-the number on a series of keys of any known form of sender or controller. Such a keyboard and the detail circuits thereof not being material to the invention are not shown in the drawing, but there is shown for convenience in tracing the sequence of operations the immediate Cir-- cult connections of a well-known counting relay sender effecting the operation of the selector switches. Under the control of such menses final selector brushes are adjusted to the terminals of this line.

In a manner to be described more in detail later, the test relay 301 (Fig. 8) of the line selector 401 is ordinarily rendered effective immediately after the adjustment of the line selector 01 to testthe condition of the selected line. But if it should be. desired that the connection shall be established to this line regardless of whether or not it is busy, there'is brought into operation a no test relay 302 (Fig. 3) which prevents the test relay 301 from performing its function, and which also operates to apply the busy condition to the selected line, this latter function of the relay 302 being effected independently of the means for applying the test condition ordinarily provided by and in the operation of the test relay 301. In a. no test operation relay 302; as will appear more in detail later, is energized a moment utter the selector brushes are adjusted, a circuit path being provided for thi purpose over the incoming trunk line from the sender (Fig. 5). If it had been desired by the toll operator that the connection be made regardless of the line condition, she would have instructed the incoming operator to that effect, and the latter oyxzrator. preterably before operating the sender. would have depressed the no test key More in detail, the operation of the system is as follows:

Subscriber 100 desiring to initiate a toll call removes his receiver from the switchhook and causes thereby in the well-known manner the automatic or manual extension of his line 10% to an operators cord circuit 101. The operator having learned by means of her telephone set (not shown) the number of the desired subscriber, transmits this numloer to an incoming or recording operator over an order wire (not shown) and extends line 10$ by inserting plug 102 into jack 103 to a

trunk line

105, 106 in accordance with instructions received from the incoming operator. A circuit is closed now from ground through resistance 10?, sleeve contacts of jack 103 and plug 102, and the coil of relay 108 to grounded battery, and the potential on the'n'iultiples of the sleeve of jack 103 is reduced to guard

trunk line

105, 106 against other incoming calls. A further circuit is closed from one sideof battery 203 through the upper winding of relay 204. upper contact of relay 205, primary winding of induction coil 200, trunlnline 105, tip side of jacl 103 and plug 102, cord circuit 101 including the winding of supervisorv relay i called subscriber 400.

109 and back through the ring side of plug 102 and jack 103, trunk line 106, primary of induction coil. 206, lower contact of relay 205 and lower winding of relay 204 to the other pole of battery 203. Relays 109 and 204 become energized, the former causing the lighting of supervisory lamp 110. and the latter the energization of relay 207.

The incoming operator proceeds now to cause the building up of a connection between the calling subscriber 1.00'andthc First she depresses her assignment key 202 closing a circuit from ground through key 202, sequence switch spring 208, (in position 1), and power magnet of sequence switch 200 to grounded battery. Sequence switch 200 leaves its first position and moves under the control of the normal spring 209 into position 13. In position 2 of sequence switch 200 a circuit is closed from ground through sequence switch spring 210, conductor 211, spring 503 of sequence switch 500 (in position 1) and winding of relay 504 to grounded battery 505. Relay 504 upon energization closes a circuit through its armature and front contact and sequence switch spring 506 for the power magnet of sequence switch 500, and this sequence switch is under the control of its normal spring 507 moved into position 13. After sequence switch 500 leaves its first position relay 504 is maintained energized through the right hand top contact of sequence switch spring 503, con ductor 510 and sequence switch spring 211 to ground. While sequence-switch 500 is -moving from position 1 to 13, circuits are established causing cord finder 501 to hunt with its wipers '508 and 509 forconductors 212 and 213'assigned by the incoming operator, and after the cord finder brushes have been set, the incoming operator sends out the first set of numerical impulses designating the called line and causes, in the wellknown 111l.!111I, SW1iCl1 201 to engage with its

wipers

214, 215 and 216 the contacts in which terminates

trunk

217, 218 and 219 leading to the final selector or connector 401. The setting of the selector switch 201 is ac- COlIlDllSllGCl before sequence switch 200 reaches position 13.

In position 12 of sequence switch 200 and position 13 of sequence switch 500, a circuitis closed from grounded battery 220 through the coil of relay 221, sequence switch'spring 222 (in position 12), sequence switch spring 223, conductor 213, cord finder brush 509, sequence switch spring 515 (in position 1 to 18 and 13), resistance 516, windings of counting relay 517, and back contact and armature of relay 518, to ground. Relay 221 by attracting its right-hand armature prepares a locking circuit for itself and when sequence switch 200 reaches its 13th position, this locking circuit is completed :sition 13 to 17). I

i/Vhen the wipers of selector switch 201 are I through sequence switch spring 222 (in po set, a circuit is closed from ground through the left-hand armature and front contact of relay 221, bottom contacts of sequence switch spring 224, wiper 214, conductor 217, sequence switch spring 303 (in positions 1 to 71} and 1, 7), conductor 304 and winding of relay to grounded battery 306. Relay 305 becomes energized and closes a circuit from ground through its left-hand armature and front contact, right-hand top and left-hand bottom contacts of sequence switch spring 307 and winding of relay 308 to grounded'battery 309. Relay 308 upon energization causes sequence switch 300 to leave its normal position and to move into position 6, by closing a circuit from ground through its left-hand armature and front contact, sequence switch spring 310, and the power magnet of sequence switch 300 to grounded battery. Relay 308 will not become de'e'nergized when sequence switch leaves its first position as this relay established a locking circuit for itself from grounded battery 309. through its winding,

from contact and right-hand armature, re-

sistance 311, test conductor 219, wiper 216, resistance 225 and sequence switchspring 226 to ground. Due to the closure of this circuit the potential on the terminal of conductor 219. is reduced to guard the trunk selected by switch 201 against other selec--' tor switches. Relay 305 remains also energized when sequence switch 300 leaves its first position, a circuit being closed from grounded. battery 306, through the winding of relay 305, conductor 304, sequence switch spring 312 (positions 1 to 6), front contact and armature of relay 305, the .top contacts of sequence switch spring 303, conductor 217, wiper 214, the bottom contacts of sequence switch spring 224, and the front contact and armature of relay 221 to ground.

In position 6 of sequence switch 300, a circuit is closed for elevating-magnet 402 of connector 401 from grounded battery 403 through the winding of magnet 402, conductor 404, sequence switch spring 312, front contact and right-hand armature of relay 305, top contacts of sequence switch spring 303, trunk conductor 217, wiper 214, the bottom contacts of sequence switch spring 224, and front contact and left-hand armature of relay 221 to ground. The elevating magnet 402 attracts its armature 405 and presses thereby brush rod 406 against a roller 407 which is constantly rotating in the direction indicated by an arrow. The line wipers 408 and 409, the test wiper 410, and the interrupter brushes carried by rod 406 are under the control of roller 407, caused to move in an upward direction. The wipers 408, 409 and 410 are adapted to engage the contacts of a terminal bank 414 in which, subscribers lines terminate, and brushes 411, 412 and 41 3 are adapted to engage an interrupter ;plate 415.

Every time brush 411 engages a conducting segment and thereby in response to each step'taken by the brush, relay 517 is short cireuited and causes upon its deenergization the stcp-by-step release of the impulse sending arrangement (not shown) set by the incoming operator. This short circuit may be traced from ground through the armature and back contact of relay 518, windings of relay 517, resistance 516, right-hand contacts of sequence switch spring 515, cord finder brush 509, conductor 213, sequence switch springs 223 and 222, wiper 215, trunk conductor 218, sequence switch springs 315 and 316, conductor 317, conducting segment 416, brush 411, conductor 417, brush 413, conducting segment 418, conductor 419, sequence switch spring 318, (position 5%,; to 6), conductor 319, and front contact and armature of relay 305 to ground.

After the impulse sending mechanism has returned to normal and thereby the wipers of connector 401 have been moved a number of steps as determined by the set position of the impulse sending mechanism, a circuit (not shown) is closed for relay 518. Relay 518 attracts its armature and causes sequence switch 500 to move out of position 13 into position 16, sequence switch spring 525 being closed in position 13 of the sequence switch. A circuit is now closed from ground through sequence switch spring 526, cord finder brush 508, conductor 212, sequence switch spring 208 and the power magnet of sequence switch 200 to grounded battery, and this sequence switch is moved into its fourteenth position. Sequence switch 200 is driven out of position 14 into position 16 by a circuit from ground through sequence switch spring 220 (bottom), armature and front contact of relay 207, sequence switch spring 227 and the magnet of thesequence switch to grounded battery. \Vhen sequence switch 200 leaves its position 13, the locking circuit of relay 221 is opened at sequence switch spring 223, and relay 221 in turn opens the energizing circuit of the elevating magnet of connector 401, the circuit of the latter being open also at sequence switch spring 224. The circuit of relay 504 is also opened at 211, this relay de'energizes and drives sequence switch 500 into its normal position, the circuit being closed from ground through the armature and back contact oi'relay 504, spring 506 and magnet of sequence switch 500 to grounded battery. When sequence switch 500 leaves its position 16, which happens after sequence switch 300 has moved out of position 7 the operators sendin device and cord finder 501 are restored to normal.

Upon the deenergization of relay 221 and the opening of spring 224 in position 14 of sequence switch 200, relay 305 becomes deenergized and closes a circuit from ground through its left-hand armature and back contact, sequence switch spring 307 (

positions

6 and 2 to 1-0), and the power magnet of sequence switch 300 to grounded battery.

Sequence switch 300 is moved into positionminus pole of battery 229. The energization of relay 305 causes sequence switch 300 to move into position 8, the circuit being closed through the left-hand armature and front contact of relay 305 and the right-hand contacts of sequence switch spring 307.

Due to the, de'e ne'rgization of 1nagnet402, t

the wipers 408410 are arrested on the contacts in which the called subscribers line terminates. The brush rod 406 with wipers 408, 410 is maintained in its advanced position by a spring pressed pawl 424 adapted to engage openings in rod 406.

If the called subscriber is idle 6., if full battery potential exists on test terminal 425, test relay 301 becomes energized, a circuit being established from grounded battery 426, through the winding of cut-off relay 427, test conductor 428, terminal 425, wiper 410, conductor 429', sequence switch spring low resistance winding of marginal. test relay 301, the bottom contacts of sequence switch spring 326 and high resistance winding of relay 301 to ground.

Relay 301 closes a locking circuit for itself from ground through right-hand armature and back contact of relay 302, upper armathereby rendering the line of subscriber 400 inaccessible to other incoming calls.

Relay 301 being energized, a circuit is closed from ground through the left-hand armature and back contact of relay 302, lower armature and front contact of relay 301, conduetor327, sequence switch sprin 310 (

position

7, 8,14) and power magnet 01 sequence switch 300 to grounded battery.

Sequence switch 300 moves out of positions into position 16. In position 15 of thes asse ses quence a ground is placed over sequence switch spring 328 on the winding of relay 302, and this relay becomes energized 1n parallel with the low resistance winding of test relay 301. Relay 302 by attracting its right-hand armature opens the locking circuit of relay 301 and closes a locking circuitfor itself. During the conversation the called subscribers line is guarded by the test circuit closed through the winding of relay 302.

When sequence switch 200 came into position 16 a circuit was closed from grounded battery 230, through sequence switch spring 231, winding of relays 232 and 228, sequence switch spring 233, and front contact and armature of relay 204 to ground. 228 becomes energized, relay 232, however, remains deenergizcd, its winding being shunted through its armature and back con tact, and the armature and back contact of ringing relay 234. When sequence switch 300 comes into position 16, ringing current is applied to the called subscribers line from ground through upper armature and front contact of relay 228, right-hand contacts of sequence switch spring 224, the talking conductors (indicated in heavy lines), the bell at the subscribers station 400, sequence switch spring bottom armature and front contact of relay 228 sequenceswitch spring 236, winding of ringing relay 234 and ringing current generator 237 to ground. Bela 234 does not become energized until the called subscriber removes his receiver from the switch hook. Upon the energization of relay 234, the shunt is removed from relay 232, this relay becomes energized and closes a shunt around relay 228. Upon the restoration of the armature or relay 228, the talking conductors are closed at the back contacts of this relay and the circuit of relay 234 is opened. Relay 232 is maintained energized by a circuit from grounded battery 230 through sequence switch spring 231, winding, armature and front contact of relay 232, sequence switch spring 233, conductor 239, and front contact and armature of relay 204 to ground. Supervisory relay 238 became also energized upon the closure of the talking circuit at the called subscribers station, after relay 228 released its armatures. The circuit for relay 238 leads from the plus pole of battery 229 through the secondary winding of repeating coil 206, the talking circuit, winding of relay 238 and the secondary winding of the repeating coil to the minus pole of battery 240. A circuit is now closed from ground through'the armature and front con: tact of relay 204, front contact and armature of relay 238 and winding of relay 205 to grounded battery 241. Upon the energization of relay 205, the circuit of relays 109 and 204 are opened but relay. 204 is Relay armature and front contact of relay 205 and lower winding of relay 204 to ground. Due

to the decnergization of relay 109 supervisory lamp 110 is extinguished.

After the conversation is finished and the called subscriber hangs up his receiver, relay becomes deiinergized and (le'energizes in tu n rel: Upon the release of the armat re of relay 205, the winding of relay 204 is again included in its original energizing circuit, and relay 109 thereby causes again the lighting'of lamp 110. The operator controlling the cord circuit 10.1 pulls plug 102 out of jack 103, causing thereby relays 108, 109 and 204 to release. Relay 204 upon. deenergization, opens the circuit of relay 207, which by retracting its armature closes a circuit from ground through sequence switch spring 220, conductor 250, armature and back contact of relay 207 and winding of relay 251 which is slow to energize to grounded battery. Relay 251 closes then a circuit over sequence switch spring 227 and sequence switch 200 is moved over its 18th into its first position. In positions 17 18 of the sequence switch, selector 201 is restored in the well-known manner.

W'hen the brush 216 of selector 201 disengages the terminal of conductor 219, relay 308 becomes deenergized and closes a circuit from ground over its armature and back contact, sequence switch spring 310 and power magnet of sequence switch 300 to grounded battery and this sequence switch is moved into its 18th position. WVhen' sequence switch 300 leaves position 16, the circuit of no test" relay 302 is opened at 325 and this relay becomes deenergized. Further a circuit is closed from grounded battery 403, through the winding of release magnet 430, conductor 431 and sequence switch spring 318, to ground. Magnet 430 attracts its armature 432, causing thereby pawl 424 to disengage brush rod 406 and presses the brush rod against roller 433 constantly rotating in a counter clockwise direction. The roller 433 moves the brush rod in a downward direction and when it reaches its normal position, a circuit is closed from grounded battery through the power magnet of sequence switch 300, sequence switch spring 310, conductor 345, conducting egment 440 of interrupter 415, brush 412, conductor' 417, brush 413, conducting segment 418, conductor 419 and sequence switch spring 318, to ground. Sequence switch 300 moves out of position 18 into position 1, and opens the energizing circuit of magnet 430.

The apparatus is noW released to normal and ready for use in the building up of another connection.

, is busy, the potential on testterrnina is reduced so as to prevent the energization of test relay 301 in position 8 of sequence switch 300. A circuit is therefore closed from grounded battery 306 through the winding of relay 305, conductor 30- left-hand top contact of sequence switch spring 315, right-hand bottom contact of sequence switch spring 316, lower armature andback contact of relay 301, and back contact and armature of relay 302, to ground. Relay 305 becomes energized and closes a circuit from ground through its lefthand armature and front contact, right-hand contacts of sequence switch spring 307, and power magnet of sequence switch 300 to grounded battery, for moving sequence switch into position 14. Release magnet 430 is now energized, a circuit being closed from grounded battery 403 throughthe winding of magnet 430, conductor 431. sequence switch spring 350, back contact and lower armature of relay 301, and back contact and left-hand armature of relay 302 to ground. Under the control of magnet r30, connector switch 401 is returned to its normal position. A circuit is now closed from grounded battery through the power magnet of sequei'ice switch 300, left-hand bottom contact of sequence switch spring 310, conductor 34?), conducting segment 14.0 of interrupter 415, brush 412, conductor 4:17, brush 413. conducting segment 4:18, conductor 410. left-hand bottom contact of sequence switch spring 318, to ground. Sequence switch 300 moves into position 17 and a busy tone is applied'lo the calling subscriber's line from 351 through the top contacts of sequence switch spring 326.

The apparatus employed in the building up of the connection is restored in the same manner as above described when considering the severing of a connection extended to an idle subscriber.

In order to insure the seizure of the called line irrespective of the electrical conditions existing on the same. prior to the sending out of impulses the incoming operator depresses the no-test key 502 and causes thereby the energization of relay 530, the circuit being from grounded battery 531 through resistance 532, right-hand winding of relay 530. Relay 530 closes from grounded battery 533 through its left-hand winding armature and front contact and sequence switch spring 534 to ground, a locking circuit for itself, said locking circuit being maintained closed by sequence switch spring 534: from position 1 to 16 of sequence switch 500.

The connection is built up in the same manner as before stated until sequence switch 300 reaches position 7, and sequence switch 200 position13. A circuit is now closed from grounded battery 426 through newness the winding of cut-ed relay 427, test conduo tor 123, terminal e25, wiper llll conductor 42;), seqiiience switch spring 325, winding of no test relay 302, sequence switch spring 328, armature and back contact of relay 305, sequence switch springs 316 and 315, con" ductor 213,sequenee switch springs 222 and 223, conductor 213, cord finder brush 509, sequence switch spring 515, and right-hand armature and front contact of relay 530, to ground. Relay 302, unlike relay 301 is adapted to be energized even if the potential on test terminal 125 is lowered. Thus due to the closure of the above circuit, relay 302 hecomes energized in series with relay 427; By attracting its right-hand armature, relay 302 closes a locking circuit foritself, and by attracting its left-hand armature it closes a circuit from ground through its front con tact and left-hand armature, conductor 327, sequence switch spring 310 and magnet of sequence switch 300 to grounded battery. Sequence switch 300 moves through its eighth position into its fourteenth position. Due to the closure of thistest circuit including relay 302, no relay 301 can become energized when a connector associated therewith is set on the terminals of this called subscribers line. v

In position 16 of sequence switch 500, se- (11101100 switch 200 is driven through position 14 into position 16, and ringing current is applied to the called subscribers line in the .same manner as above described.

The apparatus is released in the same manner as above described.

It. will be seen, therefore, that in case the incoming operator depresses the no test key 502, test relay 301 becomes ineffective and no test relay 302 performs the function (rendering busy of the called line, co-, operation in the control of connector 401.

etc.) of test relay 301, irrespective of the electrical condition existing on the calledline.

)Vhat is claimed is:

1. In a telephone system, a plurality of lines, a selector switch for connecting an incoming line to an outgoing line, means operable automatically under a predetermined eleetrical condition of an outgoing line for controlling said switch and for rendering said outgoing line inaccessible to other incoming lines, independent means also ope able automatically to perform the functions of said means irrespectire of said electrical conditions, and means for rendering operative either said tirst mentioned means or said independent means.

2. In a telephone system, a plurality of lines, a selector switch for completing connections between calling and called lines, testing means operable automatically to establish busy test conditions for idle called lines and to control said switch, independan idle line is selected to control the opera I tion of said switch and to establish a busy test condition for said line, a second relay operable at Wlll adapted when a line is se 'lected whether idle or busy to control said switch and to establish a busy test condition for said line. e

4. Ina telephone system, a plurality of lines, means for establishing connection between calling and called lines, a line selector and a switch for completing connections to selected-lines testing means and independent means both adapted automatically to control said switch and operative respectively upon the selections of idleand busy lines, a common controlling line means controllable over said line for rendering operative either said testing means or said independent means.

5. In a telephone system, a plurality of lines, a line selector and means for testing selected lines, a relay adapted when energized to render the testing means inefiective, a self-locking circuit for said relay, and automatic means controllable at will for initially energizing said relay before the line can be tested.

6. In a testing svstem, a plurality of lines, a line selector and means for testing selected lines, two controlling devices one adapted to render efiect-ive and the other ineffective said testing means, an incoming line for said selector, and selective means for controlling the. operat1on of said devices only over said incoming line.

- 7. In a telephone system, a plurality ofincoming lines, a plurality of outgoing lines,

a selector switch for connectin an incoming line to an outgoingline, means operative under a predetermined electrical condition of said outgoing line for controlling the operation of said switch and for rendering the selected outgoing line inaccessible to other the calling incoming line for peri 'o all irrespective of the electrical concimon c said outgoing line.

9. in a telephone system, a plurality o3. incoming lines, a plurality of outgoing l the functions of said iiist mentioned lines a selector switch for selecting outgoing line under the control of current impulses sent over said incoming line, a. relay adapted to cooperate in the control of selecting operation of said switch under a predetermined electrical condition of the selected outgoing line, and another relay controlled only over said incoming line for cooperating in the control of the selecting operation of said switch irrespective of electrical condition. I

10. In a telephone system, a plurality of lines, a plurality of ,operators positions, means for extending a calling line to an operat-ors position, a trunk line, means for connecting said calling line to one end of said trunk, means controlled from said operators position for extending the other end of. said trunk to a called line, a relay controlling the guarding of said called line against other incomin lines and cooperating in the control of said last mentioned means under a predetermined electrical condition of the called line and another relay controllable from said operators position for performing all the functions of said first mentioned relay irrespective of the electrical condition of the called line, I

In witness whereof we hereunto subscribe our names this loth'dayoi April, A. l). 19l5.

FRANK N. shaves. ALBEN antennae.