US2405339A - Equipment for observing dial tone speed - Google Patents

Description

Aug.' 6, i946. M. P; WILLIS EQUIPMENT FOR OBSERVING DIAL TONE SPEED FiledJune 6, 1944 lilies 7102i Jus] 7M@ I .ai i, l M e M .sw WMM Mmm .smb Tm .wbb Lf Jrol Lf. l, E )wmf J EME, FEEH @FE .gf .Minh l l l 1 lwwillWM. /l/ l I 1 l l l l l Ilma l/VIMW a wn S w w, mxw 3\\| /l m H. m\ C\ S n., m u w M w w 0M m J C ug. ,f 1946,

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INVENTOR ATTORNEY Patented Aug. 6, 1946 EQUIPMENT FOR, OBSERVING DIAL` TONE SPEED Y Milton Powell Willis, Dallas, Tex., assignor to American Telephone and. Telegraph Company, a corporation of New York Application June 6, 1944, Serial No. 539,019

This invention relates to equipment for making observations of certain operations of machine v switching systems, and'itv particularly relates to making observations of the vtime required' for `a dial tone to appear after a call has been initiated upon a line.

In one type of machine switching systems, when a call is initiated by taking the receiver 'ofi the switchhook, certain automatic equipment is set into operation to `connect the line to an idle'rst selector. As soon 'as such iirst selector has been seized, a dial tone is sent out over the' line to indicate to thesubscriber that he may proceed to dial.

'Ihe time required for the dial tone to appear varies as between different lines in the same exchange and it also varies from time to time for any given line. In the case of a given line, the time required for the dial tone to appear willdepend upon a number'of factors. For example,if the group in which the line is located is operating under overload conditions a longer time will be required before a line nder or trunk selecto-r will become available to extend the line to a first selector. Another factor that may aect the dial tone time is the number `of lines in each group served by a given amount of appropriate switching equipment. Likewise any change in the amount of switching equipmentavailable to all the lines of such a group-will affect the time for the dial tone to appear.

As between lines in different groups the time required for the ydial tone to appear `will on the average be affected by (a) the number of -lines in each group, (bi) the amount of equipment available to serve a particular group, and (c) the load on the lines of each group. Any one or all of the foregoing factors may, of course, vary from group to group.

Due to these and other conditions it is desirvable to have means available to make observations ofthe time required for the`dial tone to appear n each of a number of lines selected as samples for observation. In accordance with the present invention the lines selected for sampling purposes are connected to contacts of a rotary switch, which may be used by the service observing operator to connect her equipment to the lines one at a time, under conditions simulatingv the conditions of a call. As connections are thus successively established to the lines the service observer may note the time required beforethe dial tone appears for each line. If desired, the lines taken for sampling .may be more or less uniformly chosen from groups which `are subject lto diner- 1'2 Claims. (Cl. 179-1752) 2. ent service conditions, so that the diierence in dial tone time between lines of'different groups may be noted.

In the system as/herein disclosed, the switch which is used for service observing purposes is of a type having six brushes and twenty-two point banks for each brush. It will be understood, however, that other types of switches mayequally well be used.

The invention maynow be more fully vunderstood from the following description, when read in connection with the accompanying drawings, in which Figure 1 illustrates the invention as applied to a system in which the lines-to be observed are operated on either a flat rate or message vrate basis; while Fig. 2 shows the system as applied to observed lines which are provided with coin box equipment at the subscribers stations.

Referring-to Fig. l, aswitch SW is shown having six wipers Wi to We, inclusive, each arranged lto operate overa bank having twenty-two points.

The brushes of the switch maybe rotated step by step to establishv connections to the different points of the switch. When the switch is operated step by step, under the control of the service observing operator as will be described later, the operators,service-observing equipmentl may be connected to successive lines to be tested, under conditions approximating the initiation of a call over each line. For this purpose the first twentyone points of bank l are connected to the tip conductors of 21 lines and the corresponding points in bank 2 are connected to the ring conductors of said lines. A busy tone is connected to the twenty-second point yof bank l. This informs the operator that the switch isvin its stand-by position ready to test all of the lines connected to banks l and 2.

In a similar manner the tip conductors of another group of twenty-onev lines (herein numbered 22 to 42, inclusive) are connected to ythe first twenty-one points of bank 3, the corresponding tip conductors being connected to the first twenty-one points of bank 4. Likewise the tip and ring conductors, respectively, of'li'nes numbered 43 to 63 are connected to the first twentyonev points of banks 5 and 6, respectively. Busy tones'are applied to points 22 of banks'3 and 5 to indicate to the operator that the switch is in its waiting position ready to test the linesconnected to those banks. After all of the lines connected to a pair of banks have been'tested, the busy will be heard on kthe next step to indicate that the switch is again in its Astand-'by position.

The conductors vIIJI and 102, leading'towipers W1 and W2 of the switch SW, are connected over trunk TL1 and through tip and ring terminals of an intermediate frame IDF to tip and ring contacts of a nal selector FS. The final selector FS is normally employed in the exchange for establishingconnections from line to line, but certain of its terminal points are for purposes of the present invention assigned to trunks such as TL1. signed to other testing trunks such as TLz and TL3.

When the service observing operator wishes to connect her set OS to any of the lines I to 2|, inclusive, for testing purposes, the receiveris removed from the hook of the set and this causes a line nder LF or other suitable mechanism (herein indicated symbolically) to establish connection between the operators set and the iirst lselector of the central o iiice switching apparatus CS. The operator then dials by means of the oflice dial OD the special number assigned Vtrunk TL1, thus completing a connection through the central oice switching apparatus CS and the iinal selector FS to the tip and ring terminals of the trunk TL1.

`lf access to trunk TLz 4is desired the operator may, by dialing a diierent code, connect her set to the tip and ring terminals in the iinal selector FS which are connected to the trunk TLz. As this trunk Vis associated with conductors |03 and |04 leading to wipers W3 and W4, access is thus given to lines 22 to 42 for testing purposes. By dialing a still different code the trunk TLs may be reached and this trunk is associated through conductors |05 and |06 with the banks 5 and 6 through which subscribers linesV 43 to 63, inclusive, are reached.l

,The trunks TL1, TLzY and TLa have associated with them relays BB1, BRz and BRS, respectively. The armature of relay BR1 closes a connection between conductors and |02 through a 40G-ohm resistance to the wipers W1 and W2. Consequently, when these wipers rest upon the points associatedwith one of the lines to be tested, the circuitof that line is closed in a manner similar to that occurring when a subscriber takes the receiver ofi the switchhook. In a similar manner relay BR2 closes the circuit of conductors |03 and |04 and the relay BR?. closes the circuits of conductors |05 and |06 through 400-ohm resistances.

vThe sleeve terminals of the intermediate distributing frame lDF, which are associated with the trunks TL1, TLz and TLS, are strapped together so that when the final selector FS establishes a connection to any one of these trunks, a circuit is completed over a common sleeve conductor SC to operate a relay SR which controls the circuit of a relay ST. The operator is also provided with a key K which, if closed when the relay SR is operated, will complete a circuit through the relay ST, which in turn controls the operation of a stepping magnet SM for the switch SW.

Further details of the `apparatus will be clear from a description of the operation. Let us assume that the switch SW is insuch position'that each of its six wipers ,is resting upon the twentysecond point in the corresponding bank of the switch. The operator through herset closes the OperatOrS line 0L, thus causing the line finder, or other switching apparatus, to connect the line OL to the first selector of the central oce switching apparatus CS. As soon as the connection to Other terminal points are similarly as-v hear a dial tone indicating that the circuit is in condition to be dialed. The operator then uses her dial OD to dial the code of the trunk TL1.

In response to this dialing operation the nal selector FS connects the operators line OL to the terminals of the trunk TL1, thus operating the relay BB1. As soon as the nal selector FS makes connection with the trunk TL1 a busy tone is transmitted over point 22 of bank of the switch SW, over conductor |0I, through a condenser and over the tip conductor of the trunk TL1 and the operators line OL to the operators set OS. This informs the operator that each of the wipers of the switch SW is resting upon the twenty-second point of the corresponding switch bank. At the saine time the connection above described was established over the trunk TL1 a con- /nection is completed from the sleeve circuit of vthe central oiiice switching equipment CS, over the common sleeve conductor SC, and through the.` winding of the relay vSR. to battery B, thus enel*- gizing the relay SR. Y.' j

The operator, upon hearing the busy tone above described,` closes the key K momentarily, thus establishing a circuit from ground, over the upper contacts of said key, over conductor H0, over the now .closed contact of relay SR., and through the winding of relay ST to battery B. Relay ST upon being energized closes a circuit from ground over its contact to energize thestepping magnet SM. As soon as the key K is restored, relay ST is'released, thus opening the circuit of the stepping magnet SM which advances the six wipers of the switch SW to the rst point in each of the switch banks.

A connection is now established for the iirst line to be tested from the tip conductor of said line I, over wiper W1, conductor |0|, over the closed contact of relay BR1, over conductor |02, through a tLOU-ohm resistance, and thence over wiper W2 to the ring conductor of line This completes the circuit of line I, thus causing the line nder or other switching equipment (not shown) of the central ofce to establish a connection from the 1ine to a rst selector. When the connection to the rst selector is established, the usual dial tone is transmitted over the tip conductor of line l and thence to the operators set OS over the circuit previously traced for the busy tone from point 22 of switch bank The operator notes the time elapsing from the moment the key K is released to the moment when the busy tone is heard, and thereby knows the time requiredfor a subscriber initiating a call on `that line to hear the dial tone. f V

In a similar manner the operator, by again depressing the key, will operate the stepping magnet SM to advance each wiper of'the switch SW to the second point of each bank. Thereupon the time elapsing before the dialtone is heard'may be noted for line No. 2. As soon as the operator notes down the elapsed time for line No. 2, the operator in a similar manner advances the wipers of the switch SW1 over successive points of the banks until all of the lines to 2 inclusive, have been tested. After line 2| has been tested the next operation of the key .K advances theA wipers of the switch to the twenty-second point of each bank, and the operator again hears the busy `tone coming in over point 22 of bank This apprises the operator that the rst set of twenty-one lines has been tested.

` The operator now releases the connection to trunkIL1 and dials the code number by which the trunk TL2 may be reached Relay-BR1 vis. released as soon as the brushes of the inal'selector messe FS leave the terminals of the trunk T111. When said brushes of a nnal selector in response to the dialed code establish contact with the terminals of the trunk TLz the relay BH2 is energized, and relay SR1 is operated over the sleeve terminal of the trunk TLz at the iinal selector FS. The operator now hears a busy tone over the twentyesecond point of bank 3, over conductor 103, through the condenser associated with the relay BRz, over the tip conductor of the trunk TLz, and thence over the circuit previously traced to the operators set OS.

The operator again actuates the key K, stepping the wipers of the switch SW to the second point of eachV of the banks. A circuit is thus completed over the operating contact of the relay- BH2 through a' 40C-ohm resistance, and thence over the wipers -W3 and` W4 to the tip and ring conductors ofline 22. After the operator notes the dial tone coming in over line 22, the key K is again actuated to advance the switch to the next line, andso on, until the dial tone time of each of the lines 22 to'42 has been determined.

Thev next operation of the key K` advances the wipers of the switch again to the twenty-second point so that the operator once more hears the busy tone. The operator now releases and then dials the code for trunk TLa, thus establishing connection to wipers W5 and We of the switch SW. Upon hearing the busy tone from the twenty-second point of bank 5, the operator then actuates the key K to step the switch SW step by step until all of the lines 43 to 63 have been tested.

The foregoing operations may be repeated from time'to time to test the dial tone times of the various lines at different times of day and under different conditions of load. From the observations thus made information may be tabulated to inform those concerned of the operating conditions in the exchange so far as the waiting time for dial tones is concerned. As already stated, the lines chosen for test purposes and connected to the various points of the switch SW may be representative of 'different groups, if desired, so that information may be had as to the dial tone time for representative lines under different service conditions. Also comparisons may be made between individual lines of the same group, or between lines of any group and those of any other group.

The arrangement of Fig. lis that preferably employed 'when the lines to be tested are either flat rate lines or message rate lines; Where, however, coin box lines are to be tested, a somewhat 'different arrangement, such as that illustrated in Fig. 2, is employed.

Since circuits over coin box lines cannot be completed until a coin has been dropped in a coin box to operate the coin box trunk relay equipment, arrangements must be vprovided for simulating the conditions resulting from the dropping of the coin. Therefore, in the arrangement of Fig. 2, while the points 1 to 21, inclusive, of banks I and 2 are connected to the tip and ring conductors of the lines as before, the points of bank 3 are arranged to establish a connection through an 800- ohm resistance over the wiper W3 to the ring conductors of each of the lines, to operate the coin box trunk relay equipment. Since three banks are therefore used for each service observing trunk, only two trunks, TL1 and TLz with their associated relays BB1 and BRz, are provided. The tip and ring Aconductors of lines 22 to 42, inclusive, are' in this instanceconnectedto lthe points dialed and 1511611 dial the trunk T112.

ofbanks a .and 5,1 while the.points-fontamara@ sistanceftothering'conductor-s of these# lines 'to operate: thel coinrbox trunk. relay equipment.

Otherwise,l the apparatus is lsimilar to that of Figi.-

I'n-testing-the lines thecoperator proceeds as inV thecase of Fig. 1, first` dialing .to Aestablish a connection' to ytrunk TLi, thusoperating the ..re/ lay vBB1-andthe relay SR. Upon hearing the busy tonerfrom the twenty-secondpoint of bank I, the operator momentarily closes the key-.K to operate-'the relay ST, which in turn'operates' the stepping magnet to advance the switch to theiirst pointin each bank. As before,a line circuit closing connection is established from thetip. of line I, over-ithe wiper/W1, conductor III, operating Contact oirel'ay BRi, conductor |62, through the 40G-ohm resistance; and over wiper W2 to the ring conductor of. line I.'

Howevenlthis operation alone does not `complete the 1 line circuit, for the coin 'box trunk relay equipment must also be operated before the line can be-extendedfto any switching equipment. This isdoneby means of the third bank of the switch, a ground rconnection being established throughtheBOO'ohm resistance, over wiper Wa and the iirst point of bank v3 `of the ring conductor ofrline I. Theclosing of this circuit and the simultaneous closing of the circuit over the 'rst points 'of banks vI and 2 simulate the conditions'underwhichf a vcall .is kinitiated onl a coin contrlledlinei As soon as the first selector has been reached, the operator will hear the dial tone from the line I as described in connectionV with Fig. `l. The foperatorthen 'successively tests the other lines bysteppingfthe switch point by point by means of the operators key K, as described in connection with Fig. `1.

The' operator having tested lines I to 2l, inclusive, will release the connection previously After connection to the trunk has `been established, the operator proceeds in asimilar manner to test lines 22 lto 42.

Whiler this invention has been ldisclosed in certain specific arrangements which are deemedfdesirable, it will be obvious that the general principles herein set forth may be embodied in many other'organizations, widely different from those illustrated, without departing from the spirit of the invention as defined in theappended claims.

What is claimed is:v

1. A- system for observing the time between theinitiation ofl a calll over a telephone line and the appearance of a dial tone, saidV system including a step by step switch to thevcontacts of which lines to be tested are connected, a trunk leading tosaid switch, means including iinal selectors for selecting-for communication purposes any desired line in'resp'on'se to the dialed number'as'signedto said -line andv for selecting said trunk and connecting an operators observing set thereto in response to a dialed'number asn signed to said trunk, means whereby said trunk when selected is conditioned to simulate the finitiation of 'a call, andmeans-controlled by the operator' to send a single pulse over said trunk to step said switch from: line to line to successively initiate simulated calls over Asaid lines without changing the setting ofany iinal selector, whereby the time requirement for vthe dial tone to appear maybe observed for each line connected to saidste'p-byestep switch. Y

the initiation of a call over a telephone line and the appearance of a dial tone, said system including a step by step switch to the contacts-of which lines to be tested are connected, a trunk leading to said switch, means including iinal selectors for selecting for communication purposes any desired line in response to the dialed number assigned to said lineA and for selecting said trunk and connecting an operators observing set thereto in response to a dialed number assigned to said trunk, means whereby said trunk when selected is conditioned to simulate the initiation of a call, means controlled by the operator to send a single pulse over said trunk to step said switch from line to line to successively initiate simulated calls over said lines without changing the setting of any final selector, whereby the time required for the dial tone to appear may be observed for each line connected to said step-by-step switch, and means to transmit a special signal to the operator when a group of the lines connected tothe switch have been tested. A Y j 3. A system for observing the time Vbetween the initiation of a call over a telephone line andthe appearance of a dial tone, said system ,inf cluding a step by step switch'to the contacts of which lines to be tested are connected, a trunk leading to said switch, means including :final selectors for selecting for communication purposes any desired line in response ,to ,the dialed number assigned to said line: and iorselecting said trunk and connecting an operator-s observing set thereto in response to adialed number assigned to said trunk, means whereby said trunk when selected is conditioned to simulate theinitiation of a call, vmeans controlled by. the operator to send a single pulse over said trunk -to step said switch from line to iine `to successively initiate simulated calls over said lines without changing the setting of any nalV selector, whereby the time required for the dial tone' to appear may be observed foreach line connectedtosaid step-by-step switch,` and means associated with said switch acting when the line is selected for observation to produce a condition to voperate the coin box trunk relay equipment associated with the line. Y Y

4. A system for observing the time between the initiation of a `call over a telephone line vand the appearance ,of a dial tone, said ,system including a step :by step switch to thecontactsof which lines to be tested are g connected,V a vtrunk leading to said switch, means including iinal selectors for selecting for communication purposes any desired line in response tothe dialed number assigned to said line and for selecting said trunk and connecting the operators observing set thereto in responsexto a dialed number assigned to said trunk, means whereby said trunk when selected is conditioned to simulate the initiation oi a call, means'controlled by the Voperator to send a single pulse over said trunkjto step said switch from line to line to successively initiate simulated calls over` said lines without changing the setting of any nalvselector, Awhereby lthe time requiredv for the dial tone to appear may be observed'for eachrline connected to said step-by-step switch, Y meansA associated with said switch acting when the line is `selected for observation to` produce a conditionto operate the coin box trunkl relay equipment associated with the line, and means to transmit; a Yspecial signal to the operator when a group; of the lines connected to the 'switchhavezbeentested;

CII

5. A system for observing the time between the initiation of a call over a telephone line and the appearance of a dial tone, said system including a step by step switch having a plurality of banks of contacts, tip conductors of lines to be tested connected to the contacts of one bank of said switch and the ring conductors of said lines being connected to the corresponding contacts of another bank, a trunk having tip and ring conductors leading to the respective wipers associated with bank having tip and ring conductors of lines connected thereto, means including nal selectors for selecting for communication purposes any desired line in response to the dialed number assigned to said line and for selecting said trunk and connecting an operators observing set thereto in response to a dialed number assigned to said trunk, means whereby when said trunk is selected its tip and ring conductors are connected through a resistance to simulate the initiation of a call, and means controlled by the operator to send` a single pulse over said trunk to step said switch from line to line to cause said trunk to successively simulate the initiation of calls over said lines without changing the setting of any final selector, whereby the time required for the dial tone to appear may be observed for each line connected to said step-by-step switch.

6. A system for observing the time between the initiation of a call over a telephone line and the appearance of a dial tone, said system including a step by step switch having a plurality of banks of contacts, tip conductors of lines to be tested connected to the contacts of one bank of said switch and the ring conductors ofsaid lines being connected to the corresponding contacts of another bank, a trunk having tip and ring conductors leading to the respective wipers associated with banks having tip and ring conductors of lines connected thereto, means including final selectors for selecting for communication purposes any desired line in response to the dialed number assigned to said line and for selecting said trunk and connecting an operators observing set thereto in response to a dialed number assigned to said trunk, means whereby when said trunk is selected its tip and ring conductors are connected through a resistance to simulate the initiation of a call, means controlled by the operator to send a single pulse over said trunk to step said switch from line to line to cause said trunk to successively simulate the initiation of cails over said lines without changing the setting of any nal selector, whereby the time required for the dial tone to appear may be observed for each line connected to said step-by-step switch. and means to transmit a special signal to the operator when a group of the lines connected tothe switch have been tested.

'7. A system for observing the time between the initiation of a call over a telephone line and the appearance of a dial tone, said system including a step by step switch having a plurality of banks of contacts, tip conductors of lines to be tested connected to the contacts of one bank of said switch and the ring conductors of said lines being connected to the corresponding contacts of another bank, a trunk having tip and ring conductors leading to the respective wipers associated with banks having tip and ring conductors of lines connected thereto, means including final selectors for selecting for communication purposes any desired line in response to the dialed number assigned to said line and for selecting said trunk and connecting an operators observing 19 set thereto in response to a dialed .number assigned tosaid trunk; means whereby when said -trunk -is selected vits tip and ring conductors are connected throughfa resistance to simulate the initiation .of a Acall,means controlled by the operator to send a single pulse over said trunk to step said switch from line to line to cause said t-runk to successively simulate the initiation of calls over said lineswithout changing the setting of any inal selector, whereby the time required for the dial tone to appear maybe observed for each line connected tosaid step-by-step switch, and means, associated with saidswitch acting when the line is selected for observation to produce a-condition to operate the coin box trunk relay equipment associatedwith the line.

8. A system for observing the time between the initiation of a call over a'telephone line and the appearance of a dialtone; said system including connected to the corresponding contacts of anotherbank, 4aA trunk having tip and ring con- Yductorsleading to the respective wipers associated with banksv havingV tip andv ring conductors of lines connected thereto, means including nal selectors for selectinglfor communication purposes any desired line in response to the dialed number assigned to said line and for selecting said trunk and connecting an operators observing set thereto in response to a dialed number assigned to said trunk, means whereby when said trunk is selected its tip and ring conductors are connected through a resistance to simulate the initiation of a call, means controlled by the operator to send a single pulse over said trunk to step said switch from line to line to cause said trunk to successively simulate the initiation of calls over said lines without changing the setting of any iinal selector, whereby the time required for the dial tone to appear may be observed for each line connected to said step-by-step switch, means associated with said switch acting when the line is selected for observation to produce a condition to operate the coin box trunk relay equipment associated with each line, and means to transmit a special signal to the operator when a group of the lines connected to the switch have been tested.

9. A system for observing the time between the initiation of a call over a telephone line and the appearance of a dial tone, said system including a step by step switch having a plurality of contacts, a plurality of lines to be tested, the tip conductors of certain of said lines being connected to the contacts of one bank of said switch and the corresponding ring conductors of said lines being similarly connected to the contacts of another bank, the tip and ring conductors of other of the lines to be tested being similarly connected to other banks of said switch, trunks having tip and ring conductors leading to the respective wipers associated with pairs of banks having tip and ring conductors connected thereto, there being a trunk for each pair of banks having tip and ring conductors of lines connected thereto, means including iinal selectors for selecting for communication purposes any desired line in response to the dialed number assigned to said line and for selecting any one of said trunks and connecting an operators observing set thereto in response to a dialed number assigned to said trunk, means whereby when a trunk is selected its tip and ring conductors are connected through a resistanceto simulate the initiation of a call, and means controlled by the operator to -send a single pulse over said trunk to step said switch'from line to line of the pair of banks corresponding to the selected trunk to successively simulate the initiation of calls over said lines without changing the setting of any final selector, wherebi7 the timerequired for the dial tone to appear may be observed for each line connected to said step-bystep switch.

10. A system for observing the timebetween the initiation of a call over a telephoneline and the appearance of a dial tone,'said system including a step by step'switch having a plurality of contacts, a plurality of lines to be tested, the tip conductors of certain of said lines being connected to the contacts of one bank of said switch and the corresponding ring conductors-of said lines being similarly connected to the contacts of another bank, the'tip and ring conductors of other of the lines to be tested being similarly connected to other banks of said switch, trunks having tip and ring conductors leading vto the respective wipers associated with pairs of banks having tip and ring conductors connected thereto, there being a trunk for each pair of banks having tip and ring conductors of lines connected thereto, means including final selectors Vfor selecting for communication purposes any. desired line in response to the dialed number assigned to said line and for selecting any one of said trunks and connecting an operators observing set thereto in response to a dialed number assigned to said trunk, means whereby when a trunk is selected its tip and ring conductors are connected through a resistance to simulate the initiation of a call, means controlled by the operator to send a single pulse over said trunk to step said switch from line to line of the pair of banks corresponding to the selected trunk to successively simulate the initiation of calls over said lines without changing the setting of any iinal selector, whereby the time required for the dial tone to appear may be observed for each line connected to said step-by-step switch, and means to transmit a special signal to the operator when a group of lines connected to a pair of banks of the switch have been tested, whereupon the operator may select another trunk to similarly test a group of lines connected to another pair of banks of said step-by-step switch.

11. A system for observing the time between the initiation of a call over a telephone line and the appearance of a dial tone, said system including a step by step switch having a plurality of contacts, a plurality of lines to be tested, the tip conductors of certain of said lines being connected to the contacts of one bank of said switch and the corresponding ring conductors of said lines being similarly connected to the contacts of another bank, the tip and ring conductors of other of the lines to be tested being similarly connected to other banks of said switch, trunks having tip and ring conductors leading to the respective wipersv associated with pairs of banks having tip and ring conductors connected thereto, there being a trunk for each pair of banks having tip and ring conductors of lines connected thereto, means including iinal selectors for selecting for communication purposes any desired line in response to the dialed number assigned to said line and for selecting any one of said trunks and connecting an operators observing set thereto in response to a dialed number assigned to said trunk, means whereby when a trunk is selected its tip and ring conductors are connected through a resistance to andasse simulate the initiation of a cal l, means cntrolled by the operator to sen@- Aa single pulse over said trunk to step said switch from line to' line of the pair of banks corresponding to the selected trunk to successively simulate the initiation of callsover said lines without changing the setting of any nal selector, whereby the time required for the dial tone to appear may be observed for each line connected to said step-by-step switch, and means associated with said switch acting when the line is selected for observation to produce a condition to operate the coin box trunk relay equipment associated with each line. Y

12. A system for observing the time between the initiation of a call over a telephone line and the appearance of adial tone, said system including a step by step switch having a plurality of contacts, a plurality of lines to be tested, the tip ecnductors of certainof said lines being connected to the contacts of one bank .of` said switch and the corresponding ring conductors of said lines being similarlyA connected yto the contacts of another bank, the tip and'ring conductors of other of the lines to 'betested being similarly connected to other banks of said switch, 'trunks having tip and ring conductors leading to the respective Wipers associated with pairs of banks havingtip and ring conductors connected thereto, there being a trunk for eachv pair of banks having tip and ring conductors of lines connected thereto, means includ- Vdialed number assigned to said trunk, means whereby when a trunk is selected its tip and ring conductors are connected through a resistance to simulate the initiation of a call, means controlled by the operator to send a single pulse over said trunk to step said switch from line to line ofthe pair of banks corresponding to the selected trunks to successively simulate the initiation of calls 'over said lines without changing thefsetting of vany nal selector, whereby the time required for the dial tone to appear may be observed for each line connected to said step-by-step switch, means associated with said switch'acting when the line is selected for observation to produce a condition to operate the coin box trunk relay equipment associated'with each line, and means to transmit a special signal to the operator when a group of lines connected to a pair of banks of the switch have been tested, whereupon the'operat'or may select another trunk to similarly test a'group of lines connected to another pair of banks of 'said step -by-step switch.

' M'JLTON POWELL lWII.J.[S.

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