US1482712A - Testing system for automatic exchanges - Google Patents

Description

Feb. 5 1924. 1,482,712

' F. A. STEARN TESTING SYSTEM FOR AUTOMATIC EXCHANGES vFiled. 0c 3 112* a 1 1 ,|O,H,|3,l5,|4,

//7 1/e/7 for Fran/1M7 A. 67"90/77 Patented Felt. 5, i924.

r it FRANKLIN A. STEARN, F PATERSON, NEW JERSEY, ASSIGNOR TO WESTERN ELEC- TRIC COMPlhNY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEVJ YORK.

TESTING SYSTEM FOR AUTOMATIC EXCHANGES.

Application filed October 3, 1919. Serial No. 328,207.

- and useful Improvements in Testing Sys- (Lil terns for Automatic Exchanges, of which the following is a full, clear, concise, and exact description.

This invention relates to a circuit arrangement for accomplishing a laboratory of an automatic switch to be used in telephone exchange systems.

It is the object of this invention to pro-.

vide a circuit arrangement in conjunction with suitable switching devices such that an automatic switch and certain relays which normally operate in conjunction therewith, may be tested under conditions similar to those which will be encountered in actual use.

A feature of the present invention is an arrangement whereby the test is automatically repeated any desired number of times in case each series of tests is successfully accomplished.

An additional feature of the invention is an arrangement whereby a switch is caused to advance through its various stages of operation successively and is allowed only a predetermined length of time in which to function properly. In case the switch fails to function properly at any stage, means are provided to signal an attendant. In case of failure at any stage of operation, further operation of the testing device is prevented, so that the attendant may at once observe at which stage of operation the switch failed.

it is thought that the invention will be best understood from the following detailed description, reference being had to the accompanying drawing.

At the left of the drawing is shown the automatic switch to be tested. The righthand portion of the drawing shows a circuit controlling switch which has control of the progress of the various tests. In the lower it-hand portion of the drawing is shown a series of counting relays under the control of an interrupter which measure the time allowed for the successful completion of each stage of the tests.

The invention will be shown and described in connection with a rotary step-by-step switch arranged for motion in one plane only, and adapted to be used as an individual line switch, and is, therefore, provided with a stepping magnet, line and cut-off relays, and a message register magnet. It is to be understood that the invention is to be limited only by the appended claims, since the invention may be used in conjunction with switches of many types, and switches arranged to be used to give various kinds of service.

When the attendant desires to start the test, he will depress a start key indicated generally at 1, it being understood that the controlling sequence switch 2, is normally in position 1, whereupon a circuit is completed from grounded battery, right-hand armature and back contact of relay 3, conductor 4:, power magnet of sequence switch 2, conductor 5, closed contacts 6 and 7 of start key 1, conductor 8, right-hand contact of sequence switch spring 9, right-hand armature and back contact of relay 10, conductor 11. righthand armature and back contact of relay 12, armature and back contact of relay 13, upper contacts of sequence switch spring 14, outer right-hand armature and back contact of relay 15, outer armature and back contact of relay 16, left-hand armature and back contact of relay 17, lower right-hand contact of sequence switch spring 18, conductors 19 and 20, inner upper armature of relay 21 and its back contact to ground. in response to the closure of this circuit, sequence switch 2 is moved out of position 1 and into position 2 under the control of its master contact 22.

In position 2, the line switch is caused to operate in the same manner as though a call had been originated by a substation whose line is sufhciently distant to provide a maximum line resistance.

A circuit is completed from grounded battery, winding of line relay 23, outer upper armature and back contact of cutoff relay 21, conductor 24, resistance 25, upper lefthand contact of sequence switch spring 26. conductor 20, inner upper armature and back contact of relay 21 to ground. The resistance 25 has a resistance value equal to that of a substation line of maximum length.

Assuming that the test is to progress satisfactorily, relay 23 is energized in this circuit whereupon a circuit is completed from ground, winding of stepping magnet 27, armature and back contact of magnet 27, lower right-hand contact of sequence switch spring 87, conductor 28, outer lower armature and back contact of relay 21, conductor 29, normally closed contacts 30 and 31, conductor 32, armature and front contact of relay 23, conductor 33, resistance 34 to grounded battery. Stepping magnet 27 is energized in this circuit and advances the switch brushes one step thus opening the contacts 30 and 31 and closing contacts 30 and 35. A test circuit is now completed extending from grounded battery, resistance 34, conductor 33, armatureand front contact of relay 23, conductor 36, lower winding of cut-off relay 21, brush 37 and its second contact, resistance 38, lower contact of sequence switch spring 39, left-hand armature and back contact of relay 10 to ground. Assuming that the test is to proceed successfully, cut-off relay 21 will be energized in this circuit. This is the regular circuit of the line switch, that is, idle trunks will be characterized by the presence of direct ground on their test terminals. Should cutoff relay 21 fail to function properly, normally a self-interrupting circuit for magnet 27 will be in existence from ground, winding of magnet 27, armature and back contact of magnet 27, lower right-hand contact of sequence switch spring 87, conductor 28, outer lower armature and back contact of relay 21, conductor 29, closed off- normal contacts 30 and 35, resistance 34 to grounded battery. Since relay 21 is energized,

however, this circuit is broken and the switch remains at rest with its brushes on the second set of terminals. Relay 21, upon energization, completes a locking circuit for itself extending from grounded battery, lefthand winding of relay 10, lower left-hand contact of sequence switch 40, switch brush 41 and its second contact, inner lower armature and front contact of relay21, winding of message register magnet 42, upper winding of relay 21 to ground. Relay 10 is energized in this circuit, but register magnet 42 being marginal, is not energized at this time.

It is to be observed that as soon as start key 1 is depressed a circuit is completed for relay 43 as soon as the interrupter reaches a conducting segment. This circuit extends from grounded battery, winding of relay 43, armature and back contact of rela-y 44, conductor 45, closed contacts 46 and 47 of key 1, interrupter 48 to ground. Helay 43 is energized and prepares a circuit through its lefthand armature for relay 44, but this circuit is not effective since relay 44 is shunted by the direct ground at interrupter 48. As soon as interrupter 48 engages an insulating segment, the short circuit is removed and relay 44 is energized, these relays now being locked to ground at the lower contact of sequence switch spring 49 by way of the left-hand armature and front contact of relay 43 and conductor 50. Since counting relays are well known in the art, further description will not be given of the detailed operation of these relays. However, it will be obvious that when counting relay 51 is energized, a circuit will be completed from grounded battery, winding of relay 3, left-hand armature and front contact of relay 51 to grounded conductor 50. Energization of relay 3 completes a circuit from grounded battery through the magnets of a bell 52, and the left-handarmature and front contact of relay 3 to ground. The ringing of bell 52 will attract the attention of an attendant who will observe at what stage of operation the switch failed. The right-hand armature of relay 3, upon attraction, removes the battery feed from sequence switch 2 so that the sequence switch cannot move out of whatever testing position it is in in case the switch should successfully accomplish a particular operation after the time period within which such successful operation was to have taken place has expired.

Cut-off relay 21, upon energization, opens the circuit of line relay 23 in the well-known manner and this relay deenergizes. In order to insure proper time for the deenergization of relay 21, and to afford message register magnet 42 an opportunity to operate, in case it has a tendency to operate falsely at this time,sequence switch 2 cannot be advanced out of position 2 until counting relay 53 has been energized. With counting relay 53 and relay 1O energized, a circuit is completed from grounded battery, right-hand armature and back contact of relay 3, conductor 4, power magnet of sequence switch 2, lower left-hand contact of sequence switch spring 54, conductors 55 and 56, right-hand armature and front contact. of relay 10, conductor 57, lefthand armature and front contact of relay 53 to ground for moving this sequence switch out of position 2 and into position 3.

In case cutoff relay 21 fails to operate in time to cause the switch to be brought to rest on the second set of contacts, relay 15 will be energized as soon as the brushes engage the third set of contacts. This circuit extends from grounded battery, winding of relay 15, conductors 82 and 83, upper left-hand contact of sequence switch spring 84, brush 58 and its associated contact, conductor 79, the lower right-hand contact of sequence switch spring 62 to ground. With relay 15 energized, further operation of the stepping magnet 27 is impossible since the winding of magnet 27 is now shunted by way of conductor 81, the upper left-hand ground.

contact of sequence switch spring 76, righthand armature and back contact of relay 17, and the outer lefthand armature and front contact of relay 15 to ground. The switch will therefore be held in some position beyond its second set of contacts until reset y the attendant.

In position 3, a test is made to insure that the brushes which connect the tip and ring conductors to the trunk have made good contacts and that the message register magnet has not functioned, which at this time would be improper.

A circuit is now completed from grounded battery, winding of relay 15, conductors 82 and 83, lower left-hand contact of sequence switch spring 84, switch brush 58 and its second contact, inner upper armature and front contact of cut-off relay 21, conductor 20, upper left-hand contact of sequence switch spring 26, resistance 25, conductor 24, outer upper armature and front contact of cut-off relay 21, switch brush 59 and its second contact, lower left-hand contact of sequence switch spring 60, winding of relay 16 to ground.

If either of the brushes 58 or 59 have failed to make proper contact with their respective terminals, there will not be sufficient current-flow in the above traced circuit to allow either relay 15 or relay 16 to become energized. In case proper connections have been made and in case measure register magnet 42 has not been operated, a circuit will be completed from grounded battery, righthand armature and back contact of relay 3, conductor 4, power magnet of sequence switch 2, upper right-hand contact of sequence switch spring 61, inner right-hand armature and front contact of relay 15, inner right-hand armature and front contact of relay 16, conductors and 56, right-hand armature and front contact of relay 10, which is still energized over its original energizing path, conductor 57, upper right hand contact of sequence switch spring 62 to Sequence switch 2 is caused to move from position 3 to position 4 upon the completion of the above traced circuit.

If register magnet 42 is energized in position 3, relay 16 will be shunted by ground at the armature and front contact of magnet 42, this shunt extending by way of conductor 63 to the upper right-hand contact of sequence switch spring 60. In this case, relay 16 would therefore not have been energized and the previously traced circuit for moving sequence switch 2 out of position 3 could not have been completed.

When sequence switch 2 left position 2, the locking circuits of such of the counting relays as had been energized were broken and these relays deenergized. However, as soon as sequence switch 2 arrived in position 3, the counting relays were again put into successive operation to time the duration of the test under the control of interrupter 48. The operation of these counting relays will not be further described since it is obvious that in each position of the sequence switch they are reoperated in the same manner to measure the duration of the test, and if the sequence switch remains unduly long in any one position, they will cause the alarm to be operated and will prevent further movement of the sequence switch. It will further be assumed that from this point on, all tests are successfully made.

When sequence switch 2 leaves position 3, the holding circuit of relays 10 and cutoff relay 21 is broken at the lower left-l1and contact of sequence switch spring 40 and these relays deenergize. At the same time, relays 15 and 16 are deenergized. Cutoff relay 21,.upon deenergization, completes a circuit from grounded battery, winding of relay 17, conductor 64, upper right-hand con tact of sequence switch spring 26, conductor 20, inner upper armature and back contact of relay 21 to ground. Relay 17 is energized and completes a circuit from grounded battery, right-hand armature and back contact of relay 3, conductor 4, power magnet of sequence switch 2, upper left-hand contact of sequence switch 61, outer right'hand armature and back contact of relay l5, outer right-hand armature and back contact of relay l6, left-hand armature and front con tact of relay 17 to ground, removing the .sequence switch out of position 4 and into position 6. The purpose of the test in position 4 is therefore to determine whether or not relay 21 falls off properly upon deenergization In position 6, a test is made to determine whether the switch will seize a particular line, after traveling over enough terminals to allow it to have accelerated to its maximum speed of operation.

With sequence switch 2 in position 6 and with cut-off relay 21 deenergized, a circuit is compleed from grounded battery, resistance 34, off- normal contacts 35 and 30, conductor 29, outer lower armature and back contact of relay 21, conductor 28, lower right-hand contact of sequence switch spring 87, armature and back contact of magnet 27, winding of magnet 27 to ground. Magnet 27 is energized in this circuit and con tinues to interrupt its circuit until its circuit is permanently broken by the energization of cut-off relay 21 when the desired terminal is seized. In position 6 of sequence switch 2 and while the line switch is in motion, relay 23 is energized by means of a circuit extending from grounded battery, winding of relay 23, the outer upper arma ture and back contact of relay 21, conductor 24, resistances 86 and 66 in parallel, the lower contacts of sequence switch spring a conductor 4,

26, conductor 20, inner upper armature and back contact of relay 21 to gorund. When the proper terminal is seized a circuit is completed from grounded battery, resistance 34, conductor 33, armature and front contact of relay 23, conductor 36, lower winding of relay 21, brush 37 and its associated contact, upper left-hand contact of sequence switch spring 39, left-hand armature and back contact of relay 10 to ground. Relay 21 is energized in this circuit and at its outer lower armature interrupts the circuit of magnet 27 to stop the switch. Relay 21 upon energization also completes a locking circuit for itself extending from grounded battery, left-hand winding of relay 10, upper left-hand contact of sequence switch spring 40, brush 41, and its associated contact, inner lower armature and front contact of relay 21, winding of message register magnet 42, upper winding of relay 21 to ground. Relay 10 is energized in this circuit. Relay 23 is deenergized as soon as relay 21 is energized, but being slow to release does not allow its armature to fall off before relay 10 has had an opportunity to energize. Message register magnet 42 is not energized in the locking circuit of relay 21 for the same reason as previously described.

Assuming that the desired terminal set was successfully seized by the line switch, the resultant energization of relay 10 completes a circuit from grounded battery, righthand armature and back contact of relay 3,

switch 2 and lower left-hand contact of sequence switch spring 54, conductors 55 and 56, right-hand armature and front contact of relay 10, conductor 57, upper right-hand contact of sequence switch spring 62 to ground, for moving sequence switch 2 out of position 6 and into position 7.

If the switch fails to stop on the desired set of terminals, which has been shown in the drawing as the 13th set, a circuit is completed for relay 15 as soon as brush 58 engages the 14th contact. This circuit extends from grounded battery, winding of relay 15, conductors 82 and 83, lower lefthand contact of sequence switch spring 85, brush 58 and its associated contact, conductor 79, lower right-hand contact of sequence switch spring 62 to ground. Relay 15 attracts its armatures and at its outer left-hand armature and front contact pro vides a shunting ground for magnet 27 by way of conductor 81, upper left-hand contact of sequence switch spring 76 and right hand armature and back contact of relay 17. Further advance of the switch is therefore prevented and the test is halted at this point with the switch in some position beyond position 13, until agaln put into operation by the attendant.

In position 7, a circuit is completed from power magnet of sequence grounded battery, winding of relay 15, conductors 82 and 83, lower right-hand contact of sequence switch spring 85, brush 58, and its associated contact, inner upper armature and front contact of relay 21, con

ductor 20, lower contacts of sequence switch spring 26, resistances 66 and 86, in parallel, conductor 24, outer upper tarmature and front contact of relay 21, brush 59 and its associated contact, upper left-hand contact of sequence switch spring 60 and winding of relay 16 to ground.

If either of the brushes 58 or 59 has failed to make good electrical contact with its associated terminal, the circuit just traced will not allow sufficient current to flow, due to. such bad contact, to allow relay 15 or 16 to become energized. Assuming, however, that good contact was made, relays 15 and 16 will be energized, whereupon a circuit is completed from grounded battery, righthand armature and back contact of relay 3, conductor 4, power magnet of sequence switch 2, upper right-hand contact of sequence switch spring 61, inner right-hand armatures and front contacts of relays 15 and 16 respectively, conductor 56, right-hand armature and front contact of relay 10, upper right-hand contact of sequence switch spring 62 to ground, for moving the sequence switch out of position 7 and into position 10.

The next test to be made is the test to determine whether or not the test relay which would normally be included in the circuit of av final connector switch will operate satisfactorily if supplied with the same potential which it could encounter in case a connector switch seized a busy direct line.

As soon as the sequence switch reaches po- 1 over a circuit from ground 1 closed upper contact of off-normal spring 69,

lower left-hand contact of sequence switch spring 68, resistance 67 to grounded battery. Resistance 67 corresponds to resistance which would be supplied to the multiple calling terminal of a line when busy in case this line is a busy direct line or a busy line which is the last line of a PBX. group. Current-flow in this circuit should be suli'i' cient to energize P.B.X. relay 13, and will also maintain relay 12 energized. A circuit 12 is therefore completed from grounded battery, right-hand armature and back contact of relay 3, conductor 4, power magnet ofsequence switch 2, lower left-hand contact of sequence switch spring 61,. right-hand 1,4.sa,71s

armature and front contact of relay l2, armature and front contact of relay 13, lower contacts of sequence switch spring 14 to ground for moving the sequence switch out of position 10 and into position 11. When sequence switch 2 leaves position 10, the locking circuit of relay 12 is broken at the lower left-hand contact of sequence switch spring 68and relays 12 and 13 are denerized.

g As soon as sequence switch 2 reaches position 11, relay 12 is again energized in response to the completion of a circuit from grounded battery, right-hand winding ofrelay 12, upper left-hand contact of sequence switch spring 49 to ground. In this position, a test is made to determine whether P.B.X. relay 13 will deenergize satisfactorily. In case it does, a circuit is completed from grounded battery, right-hand armature and back contact of relay 3, conductor 4, power magnet of sequence switch 2, lower contact of sequence switch spring 61, righthand armature and front contact of relay 12,right-hand armature and back contact of relay 13, upper right-hand and lower lefthand contact of sequence switch spring 14 to ground, for moving sequence switch out of position 11 and into position 13.

As soon as the sequence switch reaches the position 1111- and while the previously traced energizing circuit. through the righthand winding of relay 12 is still effective, a circuit is completed from ground, winding of relay 13, left-hand winding of relay 12, left-hand armature and front contact of re1ay12, contacts of sequence switch spring 71, conductor 70, closed upper contact of off-normal spring 69, lower right-hand contact of sequence switch spring 68, resistances 73 and 67, to grounded battery. Relay 12 is maintained energized in this circuit, but the resistance in this circuit due I to the presence of resistances 67 and 73 is such that relay 13 will not be energized if it functions properly. In this case relays 12 and 13 operate in the same manner as they would in case they were associated 'with a connector switch which had seized the terminals of a busy P.B.X. line and the resistances 67 and 73 are equivalent to the resistance which would be on such test terminal in the case of such seizure. Provided that relay 13 does not come up improperly at this time, a circuit is completed from grounded battery, right-hand armature and back contact of relay 3, conductor4, power magnet of sequence switch 2, lower left-hand contact of sequence switch spring 61, righthand armature and front contact of relay 12, armature and'back contact of relay 13. upper right-hand and lower left-hand con tacts of sequence switch spring 14 to ground, for moving the sequence switch out of position 13 and into position 14 As soon as sequence switch reaches position 14, a circuit is completed from grounded battery, winding of charge magnet 74, contact of sequence switch spring 75, lefthand armature and front contact of relay 10 to ground. Relay 74 is energized and locks up through its inner left-hand armature and front contact and the lower contacts of sequence switch spring 76 to ground. Current is now supplied to the message register magnet 42 through both windings of relay 10 in parallel. The circuit through the left-hand winding has been reviously traced and the circuit for the rig t-hand winding extends from grounded battery, right-hand winding of relay 10, outer left-hand armature and contact of relay 74, lower right-hand contact of sequence switch spring 40, thence by way of brush 41 and its associated contact to ground by way of the path previously described. Due to the fact that battery is now supplied to both windings of relay 10 in parallel, the resistance of this circuit is lowered suiiiciently to allow enough current to flow to energize message register magnet 42. If the magnet operates satisfactorily it will attract its armature, causing the operation of the message register and, at the same time, completing a locking circuit for itself by way of the upper contact of sequence switch Spring 77 and its armature and front contact to ground. This path to direct ground shunts down the upper winding of cut-01f relay 21 and relay 21 deenergizes. As soon as cut-ofi" relay 21 deenergizes, a circuit is completed from grounded battery, resistance 34, closed contacts 35 and 30 of the offnormal switch, conductor 29, outer lower armature and back contact of relay 21, conductor 28, contact of sequence switch spring 87, armature and back contact of stepping magnet 27, winding of stepping magnet 27 to ground. This circuit operates as a self interrupting circuit for magnet 27 to cause the advance of the switch to its normal position at which time the opening of the oif normal contact will break the circuit of stepping magnet 27. It is, therefore, obvious that in position 14, a test is made both of the operation of the message register magnet and of the, release of the cut-0d relay, as well as of the successful return of the switch to its normal position.

As soon as the switch reaches its normal position a circuit is completed from grounded battery, winding of relay 17, conductor 78, left-hand contacts of sequence switch spring 9. brush 58 and its first position contact, conductor 79, right-hand armature and front contact of relay 74, lower left-hand contact of sequence switch spring 62 to ground. Relay 17 is energized in this circuit whereupon a circuit is completed from grounded battery, right-hand armature and back contact of relay 3, conductor 4, power magnet of sequence switch 2, upper lefthand contact of sequence switch spring 61, outer right-hand armature and back contact of relay 15, outer right-hand armature and back contact of relay 16, left-hand armature and front'contact of relay 17 to ground, for moving the sequence switch out of position 14 and into position 15. It is obvious that relays 15 and 16 were deenergized as soon as sequence switch 2 left position 7. When the sequence switch leaves position 14 the circuit of relay 17 is broken and this relay deenergizes.

In position 15 of the sequence switch, a test is made to determine whether or not the cut-off relay will operate satisfactorily if supplied battery from a connector switch in case such of its windings are included as would be included in case it was used as the cut-off relay on a direct line, as distinguished from the lower resistance which would be obtained by a different connection of its windings in case it were used as the cut-off relay associated with a P.B.X. line.

A circuit is now closed from grounded battery, resistance 72, armature and back contact of relay 12, contacts of se uence switch spring 71, conductor 70, closed ower contact of off-normal spring 69, middle winding of cut-off relay 21, upper righthand contact of sequence switch spring 80,

upper winding of relay 21 to ground. If relay 21 operates satisfactorily, it will energize and complete a circuit from grounded battery, winding of relay 15, conductors 82 and 83, lower right-hand contact of sequence switch spring 84, brush 58 and its associated contact, inner upper armature and front contact of relay 21, conductors 20 and 19, upper left-hand contact of sequence switch spring 18 to ground. Relay 15 is energized and completes a circuit from grounded battery, right-hand armature and back contact of relay 3, power magnet of sequence switch 2, upper left-hand contact of sequence switch spring 54, right-hand armature and back contact of relay 17, outer left-hand armature and front contact of relay 15 to ground, for moving the sequence switch out of position 15 and into position 16.

In position 16, a circuit is completed from grounded battery, winding of relay 17, conductors 78, left-hand contacts of sequence switch spring 9, brush 58 and its associated contact, inner upper armature and front contact of relay 21, which is maintained energiz'ed in position 16 over its previous energizing circuit, conductors 20 and 19, upper left-hand contact of sequence switch spring 18 to ground. Relay 15 is deenergized as soon as the sequence switch leaves position 15.

In position 16, a test is made to determine whether test rela '12 deenergized in the proper manner. ssuming that it did so, a

circuit iscompleted from grounded battery, right-hand armature and back contact of relay 3, conductor 1, power magnet of sequence switch 2, lower right-hand contact of sequence switch spring 541, right-hand armature and back contacts of relays 12 and 13, respectively, upper contacts of sequence switch spring 14:, outer right-hand armatures and back contacts of relay 15 and 16 respectively, left-hand armature and front contact of relay 17 to ground, for moving sequence switch out of position 16 and into position 17. As soon as the sequence switch leaves position 16 the previously traced cir cuits for relays 17 and 21 are broken and these relays deenergize.

In position 17 a testis made to insure that the cut-off relay will release properly under the conditions under which it has just been used, that is, in case its upper and middle windings, connected in series, have been used to cause its energization, which is the method in which ground is supplied to the connector switch brush in case the cut-ofi relay is to be used as the cut-off relay of a direct line or the last line of a P.B.X. group. Assuming that the cut-ofl' relay 21 deenergizessatisfactorily a circuit is completed from the grounded battery, winding of relay 15, conductor 82, lower left-hand contact of sequence switch spring 18, conductors 19 and 20, inner upper armature and back contact of relay 21 to ground. Relay 15 is energized and com letes a circuit. from grounded battery, rig t-hand armature and back contact of relay 3, conductor 4, power magnet of sequence switch 2, upper left-hand contact of sequence switch spring 54L, right-hand armature and back contact of relay 17 outer left-hand armature and front contact of relay 15 to ground, for moving the sequence switch out of position 17 and into position 18.

In position 18 a test is. made to determine whether the cut-off relay will operate satisfactorily when its windingsare connected in the manner in which they would be connected in case this relay were to be used as the cut-ofl relay associated with a P.B.X. line other than the last P.B.X. line of a group. In this case, ground-will'be supplied to the test brush of a connector seizing such line, through the upper and mid dle windings of the cut-off relay in parallel, 1n order to produce the lowered resistance necessary for the proper operation of the .line' test relay and the P.B.X. test relay,

which are testing arrangements well-known in the art and which are represented in the present disclosure by relays 12 and 13, as previously set forth.

With the sequence switch in position 18 a circuit is completed from grounded battery, resistance 72, left-hand armature, and back contact of relay '12,'cont'acts of sei quence switch spring 71, conductor 70, closed lower contact of off-normal spring 69 and then through the middle and upper windings of relay 21 to ground and in parallel. The circuit through the middle winding of relay 21 extends through such winding and thence by way of the lower contacts of sequence switch spring 7 7 to ground. The circuit through the upper winding of relay 21 extends through the lower contact of sequence switch spring and thence through the upper winding of relay 21 to ground. Assuming that the relay operates satisfactorily, it will energize in response to the closure of the above-traced circuits, whereupon a circuit is completed from grounded battery, winding of relay 17 left-hand contacts of sequence switch spring 9, brush 58 and its associated contact, inner upper armature and front contact of relay 21, conductors 20 and 19, upper left-hand contact of sequence switch spring 18 to ground. Relay 17 is energized in this circuit and completes a circuit from grounded battery, righthand armature and back contact of relay 8, conductor 4:, power magnet of scquence switch 2, lower right-hand contact of sequence switch spring 54, right-hand armatures and back contacts of relays 12 and 13, upper contacts of sequence switch spring 1 1, outer right-hand armatures and back contacts of relays 15 and 16, left-hand armature and front contact of relay 17 toground for moving the sequence switch out of position 18 and into position 1.

As soon as the sequence switch leaves position 18, relay 17 is deenergized and prevents the sequence switch moving through position 1 and into position 2. Relay 21 is deenergized at the same time.

The apparatus is now all in its original condition and another cycle of tests will take place unless the attendant releases key 1. The test may be continued for any desired length of time.

What is claimed is:

1. In a testing system, an automatic switch to be tested, said automatic switch including a movable brush set and a set of stationary contact sets to be engaged thereby, means to operate said switch, means to test whether or not said switch will seize a desired terminal set after a minimum extent of travel, means to test whether or not said switch will seize a desired terminal set after a maximum extent of travel and after it has attained its full speed of operation, and means to test whether said brush set has made good contact with the asociated terminal sets.

2. In. a testing system, an automatic switch to be tested, said automatic switch including a movable brush set and a set of stationary contact sets to be engaged thereby, means to operate said switch, means to test whether or not said switch will seize a desired terminal set after a minimum extent of travel, means to test whether or not said switch will seize a desired terminal set after a maximum extent of travel and after it has attained its full speed of operation, means to test whether said brush set has made good contact with the asociated terminal sets, and means to automatically repeat said testing operations any desired number of times.

3. In a testing system, an automatic switch to be tested, said automatic switch including a movable brush set and a set of stationary contacts to be engaged thereby, means to operate said switch in a hunting movement, means to test whether or not said switch will seize a desired terminal set after a minimum extent of travel, means to test whether or not said switch will seize a desired terminal set after a maximum extent of travel and after it has attained its full speed of operation, and means to test whether said brush set has made good contact with the associated terminal sets.

4. In a testing system, an automatic switch to be tested, said automatic switch including a movable brush set and a set of stationary contact sets to be engaged thereby, means to operate said switch in a hunting movement, means to test whether or not said switch will seize a desired terminal set after making one step, means to test whether said switch will seize a desired terminal set after making a large number of steps and after it has attained its full speed of operation, and means to test whether said brush set had made good contact with the associated terminal sets.

5. In a testing system, an automatic switch to be tested, means to test said switch under various conditons, similar to those which would be encountered in actual practice, means to make said various tests in fixed sequence, a time-measuring device, means to start said timing device at the beginning of each of said testing operations, means to halt the progress of the testing operations if the switch fails to function properly within a specified time interval at any stage of its operation, and means to automatically continue the duration of the test for any desired length of time provided said switch satisfactorily meets all testing requirements.

6. In a testing system, an automatic switch to be tested, a relay to control the starting of said switch, a circuit for said relay, automatic means to successively close said circuit through bridges of various resistance values, and means to test the proper operation of said relay each time a bridge of new resistance value is introduced into said circuit.

7. In a testing system, a relay to be tested,

a circuit for said relay, automatic means to successively close said circuit through bridges of various resistance values, and means to test the'proper operation of said relay each time a bridge of new resistance value is introduced into said circuit.

8. In a testing system, an automatic switch to be tested, a relay to control the starting of said switch, a testing circuit in for said relay, means to successively complete said circuit through resistances corresponding to the minimum and maximum resistance values which would be used with said circuit in actual practise, and means to test the proper operation of said relay for each resistance Value.

In Witness whereof 'I hereunto subscribe my name this 30th day of September, A. D.

FRANKLIN A. STEARN.

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