US1860455A - Lineman's test set - Google Patents

Description

May 31, 1932. D|ETZE 1,860,455

LINEMANS TEST SET Filed Sept. 2, 1951 FIG./

x51? 50 RING/N6 TALK-LISTEN LISTEN o/vu' C L B 82 LR im-v5 TEST TONE (,R/NG

uwsrvron E. DIETZE ATTORNEY Patented May 3i, 1932 UNITEDSTATES PATENT OFFICE EGINHARD IJ'IE'IZE, OFWESTFIELD, NEW JERSEY, ASSIGN OR TO AMERICAN TELEPHONE I AND TELEGRAPH COMPANY, A. CORPORATION OF NEW YORK I LINEMANS TEST 'SET Application filed September 2, 1931. Serial No. 560,853.

This invention relates to test sets and more particularly to a linemans test set which'may beattached to open-wire lines to make tests of the conditions existing therein and the location of faults in the line. r

The object of this invention is to provide a test set which-may be usedin making tests on transmission lines, particularly telephone and telegraph lines, and including lines used in connection with carrierand repeater, systems. V

A feature of this inventionresides in the inclusion in a test set of this kind, of a filter which makes possible the use of this test set in connection with carrier lines.

Another feature resides-in the design of the inductance coil which makes the test set adaptable foruse in connection with repeater circuits. i V

It is common practice now when a telephone or telegraph line becomes broken, short-circuited, grounded or'some other unstandard condition occurs, for a lineman to s be sent out from'a. central station to make tests of the fault.

The lineman carries a telephone set which he can connect to the transmission line to determine the character and location of the fault.

The test set carried by the'lineman is also provided With facilities for connecting the set to transmission lines in which there is no faulty condition existing so that the lineman may communicate with and receive instructions from the wire. chief at the centraloifice.

In standardlinemans test sets heretofore used the connecting of the set with lines over which messages were being transmitted by means of carrier currents would cause un balance of the repeaters, cross-talk between carrier channels, interference with carrier channels and interference with the transmission of the messages thereover. The linenians set, being of comparatively low impedline to locate and rectify the carrier currents, short-c rcult the transmission of ance to the high frequency would have a tendency to lines and interfere with the messages. The connecting of the set to the line again would be modulated. by the lIOIl in the set thus causing cross-talk between the carrier, channels. If the lineman tried to converse with the wire chief over a carrier line the voice currents from the linemans set containing componentswithin the carrier range would be superimposed on the carrier current. Due care therefore had to be. exercised by the lineman in connecting his portable set with a line for and the central oflice thata carrier line was not selected. I If a lineman should happen to connect-his set with a busy carrier line it would cause unbalance of therepeaters and cross-talk between the lines. Test sets heretofore used were'also'of such low impedance that connection of the set into a system including repeaters would unbalance the repeaters and cause a transmission loss sufficient to cause interference with the transmission of messages.

In the present invention in which a filter has been included 'in the lin'emans testset and the impedance of the set has been in creased by the employment of a comparatively high impedance ratio in the induction coil, the test set may be connected to any trans. mission line in the system without causing unbalanceof the repeaters and cross-talk between the dilferent-channels in thecase of a carrier line, and communication, may be had by the lineman with the central olfice even though the. carrier channel is in use without interference with the carrier conversation. The only restrictions in the use of a line by *thelineman for the purpose of carrying on the purpose of establishing communication between lllS set a conversation are that the line connected with must be in its standard condition and that1 the voice channel of such line is not being use 5 Carrier currents employed in the transmission of telephone messages are usually at a frequency above 2000 cycles. The filter in the test set of the present invention therefore should be designed to cut ed at about 2000 cycles to enable a lineman and a wire chief to converse over a channel below the carrier. It is to be understood, therefore, that the filter included in the test set will cut off at a frequency below that of any of the carrier currents employed in the transmission system with which the set is to be used.

In the drawings,

Figure 1 represents a plurality of openwire lines mounted on a pole and a linemans test set connected to a pair of line wires over which communication may be had with the central ofiice;

Fig. 2 is a schematic of the test set of the present invention; and

Fig. 3 represents the test set employed as a fault locating device to locate a ground on a line and connected by an exploring coil with a line wire which has become grounded.

'The test set when used by a lineman to communicate with the wire chief may be connected as shown in Fig. 1 to the line wires 1 and 2 through the binding posts C and LR of the set byrneans of a suitable connecting de vice commonly used for the purpose, not shown in detail in this drawing but indicated so that a complete circuit may be traced through the line wires and the test set as comprising conductors 3 and 4. When the test set has been connected to the transmission lines 1 and 2, the lineman operates the key 5 to the listen-only position which, asillustrat ed in Fig, 2 is in a right-hand direction. A circuit for listening which may be traced through the schematic Fig. 2 in conjunction with Fig. 1 is thereupon established from the line wires through the set as follows: line wire 1, conductor 3, binding post C, conductor 6, left-hand winding of retardation coil 7, conductor 8, condenser 9, conductor 10. normal contacts of generator 11, conductor 12, spring contact 13, contact 14, the upper winding of induction coil 15, conductor 16, contact 17, spring contact 18, conductor 19, conductor 20, receiver 21, conductor 22, spring contact 23, contact 24, conductor 25, conductor 26, right-hand winding of retardation coil 7, conductor 27, conductor 28. spring contact 29, contact 30, conductor 31, binding post LR, conductor 4, to line wire 2. A shunt including the other two windings of the induction coll is also included in this circuit follows: from conductor 25 to conductor 32, spring contact 33, contact 34, conductor 35, the lower and middle windings of induction coil 15 to conductor 16.

If the lineman wants to talk to the wire chief, key 5 is moved to the talk and listen position which, as shown in the schematic Fig. 2, is in a left-hand direction. This operation of the key 5 will cut in the transmitter 36 of the linemans set establishing a local circuit for the transmitter as follows: negative terminal of local battery 37, battery clip 38, conductor 39, transmitter 36, conductor 40, spring contact 41, contact 42, conduc' tor 43, receiver switch 44, conductor 45, the primary winding of induction coil 15, conductor 46, battery clip 47, to the positive terminal of local battery 37.

The talking and listening circuits of the set when the key 5 is in the talk-listen position may be traced as follows: line wire 1, conductor 3 to the C binding post, conductor 6, lefthand winding of retardation coil 7, conductor 8, condenser 9, conductor 10, normal contacts of generator 11, conductor 12, spring contact 13. contact 48, conductor 35, the primary and secondary windings of induction coil 15, conductor 16, contact 17, spring contact 18, conductor 19, conductor 20, receiver 21, conductor 22, spring contact 23, contact 24. conductor 25, conductor 26, right-hand winding of retardation coil 7 conductor 27, spring contact 49, contact 50, conductor 31 to LR. binding post, conductor 4, to line wire 2. The local circuit for the transmitter 36 is closed by the operation of key 5 as above described and is operative with this talklisten circuit.

A buzzer 51 is provided in the linemans test set so that the lineman may be signaled by the wire chief. When the lineman wishes to place his test set in condition so that the buzzer 51 may be operated from the central oflice, he connects the conductor 3 leading from the line wire 1 to the binding post BZ and moves the key 5 to the listen-only position. This connection puts the buzzer 51 in circuit with the line as follows-: line wire 1. conductor 3. to the binding post BZ. conductor 52. buzzer 51. conductor 53, conductor 26. right-h and winding of retardation coil 7, conductor 27, conductor 28. spring contact 29, contact 30. conductor 31. binding post LR, conductor 4. to line wire 2. \Vith the circuit established as abO"8 described. the wire chief may cause operation of the buzzer 51 in the linemans test set to indicate to the lineman that the wire chief wishes to converse with him. On operation of the buzzer 51. the lineman will change the line connection from the binding post BZ to either binding post C or binding post L, leave the key 5 in the listen-only position or move the key 5 to the talk-listen position, and receive whatever instructions the wire chief wishes to transmit to him.

Should the lineman be working in a system in which no carrier lines and no repeaters 3T are'used, he may be in orderto reduce the impedance in the set, use the binding post L in place of the binding post C for connecting to the line wire 1. By connecting to the line wires in this manner, the left-h and winding of the retardation coil 7 and the condenser 9 are eliminated Assuming that the binding :post L is employed in place of the binding post C and that the key 5 has been moved to talkdisten position. the communication circuit would be as followszln from the line wire 1 to binding post L, conductor 57, conductor 10, normal contacts of generator 11, conductor 12, spring contact 13, contact 48, conductor 35, the primary and secondary windings of induction coil 15, con ductor 16, contact 17, spring contact 18, conductor 19, conductor 20, receiver 21, conductor 22, spring contact 23, contact 24, conductor 25, conductor 26, right-hand winding of retardation coil 7, conductor 27, spring contact 49, Contact 50. conductor 31, to the binding post LR, conductor 4. out to the line wire 2. The movement of the key 5 to talk-listen position also completes the local the transmitter 36.

The binding post B is provided so that the set may be used in making D. C. continuity tests. In making such tests the binding post B and binding post LR of the set are .employed and the key 5 ismoved to the listen only position. Assumingthat such a test is to be made in metallic system the binding circuit for post B of the set is connected to one of a pair of line wires and the bindingpost LR of the set is connected to the other line wire of the pair. The following circuit is thereupon completed through the set. Infrorn the line wire 1, conductor 3. binding post Brconductor 58, conductor 39, battery clip 38, battery 37. battery clip 47, conductor 46, the primary and secondary windings of induction coil 15, conductor 16. contact 17. spring contact 18. conductor 19, conductor 20. receiver 21, conductor 22,, spring contact 23, contact 24, conductor 25. conductor 26, right-hand winding of retardation coil 7. conductor 27. conductor 28, spring contact 29, contact 30, conductor 31, binding post LR, conductor 1 to line wire 2. Upon completion of this circuit the receiver in the test set will: produce a click if the line is in normal condition. Ifa D. C. continuity test is to be made on a single wire or ground system the same binding posts of the-set are used, one of the binding posts being connected to the line to be tested and the other binding post connected to ground.

A generator 11 is provided in the linemans set for ringing through the line to a central station and also for making tests through an exploring coil 59 as will be later explained.

mien the lineman is working on a line in a local battery system and wishes to communicate with the central office, he connects the binding post L and binding post LR of the test set to a pair of the line wires. He

8 then operates the key .60 to the right or AC then generates an A. C. ringing current over a circuit as follows: contact6l of the generator 11, conductor 62, conductor 80, con

tact 81 spring contact 82, conductor 83, contact 84, spring contact 6 1, conductor 25, conductor 26, right-hand winding of retardation coil 7, conductor 2?, conductor 28, spring contact 29, contact 30, conductor. 31, to binding post LR, conductor l and then out to the line, in from the line through conductor 3, to binding post L, conductor 57, conductor 10, spring contact 65, cont-act 66, to the opposite side of the coil of generator 11.

For composite ringing over the line the key 60 is set in the position shown in Fig. 2 and the set is connected to the line wires through the binding posts C and. LR. A ringing circuit through the commutator 85 and brush'86, of the generator 11 is then as follows: line wire 7 1, conductor 3, binding post C, conductor 6, left-hand winding of re tardation coil 7, conductor 8, condenser 9, conductor 10, spring contact 65.01 generator 11, contact 66, commutator 85, brush 86, conductor 87, conductor 83, contact 84:, spring contact 64, conductor 25, conductor-26, righthand winding of retardation coil 7, conductor 27, conductor 28, spring contact 29, contact 30, conductor 31, binding post LR, conductor 1 to line wire 2.

In addition to using the set for communicating with the central oliice, the lineman uses it for testing a lineand locating faults up coil 69 to determine the direction of a fault inthe line wire relative to the exploring coil 9 Theexploring coil 59 is of the type disclosed in O. A. Shann Patent 1,724,973 and is used in the same manner as described therein; for instance, when a test is to be made for a ground. on a line wire, the exploring coil 59 is connected by means of a cable 91 to the line wire 71 as shown; in Fig. 3 at the points ,67 and 68 and the pick-up coil 69 is inductively associated with the line wire 71. The test set is then connected to ground through the binding post LR, usually by means of a ground connecting device carried by the lineman. The switch 70 is then t l own to the-right as shown in Fig.2. The key 60 is moved to the left and the key 5 is thrown to the listen only position. The lineman while listening with the receiver 21, op-

erates the generator 11 to put current over the line wire 71. Assuming that the ground on the line wire 71 is to the right of the exploring coil 59 and the connection 68 as shown at 72 in Fig. 3, current from the generator 11 will flow through conductor 10, condenser 9, conductor 7 3, left-hand contact 7 4 of switch 70, conductor 75, contact 68 through line wire 71 to ground at 72 and no tone will be produced in the receiver 21. This will indicate to the lineman that the ground on the line wire 71 is in the direction to the right of the exploring coil 59. To make certain of this fact, however, the'lineman will throw the switch 70 to the left and operate the generator 11 again. Current from the generator 11 will then flow through conductor 73, contact 76 of switch 70, conductor 77 and enter the line wire 71 at 67 to the left of the pick-up coil 69 and travel in a right-hand direction to the grounded point 72 in the line wire 71. Current will then be induced in the pick-up coil 69 to operate the receiver 21. A tone will then be produced by the receiver 21 which will indicate to the lineman that the current from the generator 11 is passing in a righthand direction from the connection 67 and hence to the right of the exploring coil 59 and that the ground on the line wire 71 is in that direction. Assuming that the switch 70 is thrown to the right, as shown in Fig. 2 the circuit including the generator 11 and the line wire 71 under test is as follows: grounded binding post LR, conductor 81, contact 30, spring contact 29, conductor 28, conductor 27, right-hand winding of retardation coil 7, conductor 26, conductor 25, spring contact 64, contact 63, conductor 62, contact 61, through the coil of the generator 11, contact 66, spring contact 65, conductor 10, condenser 9, conductor 73, operated contact 74 of switch 70, conductor 75, contact 68 to the line wire 71' under test to ground 72. With the switch 7 O thrown to the left, the circuit including the generator 11 and the line 71 under test will be the same as above described with the exception that instead of the cur rent from the generator 11 passing over the conductor 75 from switch 70 through the contact 68 and the line wire 71, current will pass through contact 76, of switch 70, con ductor 77, to contact 67 on the left-hand side of the pick-up coil 69 to the line under test and to ground. In making such tests the movement of key 60 to the left closes a shunt path across the generator 11 from contact 61 through the commutator 85, brush 86, con ductor 87, spring contact 88, contact 89, conductor 90, conductor 57, conductor 10, spring contact 65, contact 66 to the other side of generator 11.

When the receiver 21 is to be used in connection with the exploring coil 59 for making tests, the inductive circuit including the pickup coil 69 and receiver 21 is closed by moving the key 60 to the left. This circuit is as follows: contact 78, conductor 79, through the pick-up coil 69, conductor 20, receiver 21,

conductor 22, spring contact 23 which is closed being used in the transmission of messages,

the'filter comprising the coils 7 and the condenser 56 offers a sufiiciently high impedance to the comparatively high frequency carrier currents to prevent unbalance of the system by the set. verse with the wire chief over a channel below that of the carrier.

By increasing the impedance ratio of the induction coil in the set especially for the listen-only condition so that the total impedance of the set is sufiicient substantially to prevent the entrance into the set of current from a system in which repeaters are employed, connection of the set to a s stem including repeaters may be accomp ished without causing unbalance of the system. The induction coil 15, therefore, included in this test set is of such high impedance as to raise the total impedance of the set to an extent to prevent unbalance of the system including repeaters.

Vith the impedance'of the test set'raised by designing the induction coil of sufliciently high impedance coil to prevent unbalance of a system employing repeaters and the inclusion of the filter which will prevent unbalance of the repeaters, cross-talk between the channels and interference with the carrier channels on lines over which carrier currents are being used in the transmission of messages, the test set may be connected to any transmission line and communication had between the lineman and the wire chief at the central ofiice.

To further disclose this invention and show the effect of bridging the linemans test set equipped with the filter as described, across a carrier line the following mathematical formulae are presented which show how the modulated current in the carrier line produced by the connection of the test set to this line, is reduced by the filter.

Assuming that the set is connected to a pair of line wires through the binding posts C and LR as shown in Fig. 1 and that the line wires are carrier lines. Then let, Z =Characteristic impedance of filter Z Impedance of filter terminated in Z =Impedance of filter terminated in Z 0c =Attenuation of filter Z =Impedance of line Z =lmpedance of test set The lineman, however, may con- ,a =Voltage amplification factor of test set acting as a modulator E =Voltage generated in the carrier line Current delivered into filter:

(assuming fiiter terminated in Z Current delivered into test set:

Voltage applied across test'set:

Modulated voltage generated by test set:

E7 M O Modulated current into filter: (assuming filter terminated in Z El Z Z Modulated current in line with filter in test set: V

( L+ o) (ZA+ZS) (QZBIPZL') l line'wire; means for sending a test current Impedances marked apply at frequency of modulated current.

In a similar way, the modulated current in the line without the filter in the test set:

The ratio gives the reduction due to the filter 1n the modulated current produced by the test set.

When at all frequencies Z =Z it is also Z =Z and this ratio ion a.

The filter in addition should be designed to present a high impedance when viewed from the line so as to prevent transmission loss orunbalance of the repeaters. The condition that Z O =Z therefore may not represent the best design of the filter, and it may be neces sary to have Z 0 Z I In that case the general formulae given above instead of the simple expression;ev 2a, has to be used in computing the modulated current by the filter.

What is claimed is 1.- A linemans telephone set to be connected to linesin a signaling system in which carrier currents are employed in the trans- 2. A linemans telephone set to be connected to transmission lines in a signaling system in which repeaters are employed 1n the transmisslon of signals, sald telephone set including an induction coil which pre vents unbalance of the repeaters and prevents a transmission loss suflicientto interfere with the transmission of messages.

3; A linemans test set including means for connecting. the test set to a line wire of a signaling system for testing the condition of the line wire means for sending test currents over the line wire-means for connecting the test set to otherline wires of a signaling system so that communication maybe had between a lineman and an attendant at the central office and a filter in the test set to prevent cross-talk between carrier channels and interference with carrier conversations 4. A linemans test set including an exv ploring coil for connecting to a line wire of a signaling system to test the condition of the ofiice, and a filter in the test set designed to prevent modulation of carrier currents b the iron in the test set to prevent crosstallx between carrier channels should the lineman connect the set system. r g

5. A linemans test set including an exploring coil for connecting to a line wire of a signaling system to test the condition of the line wire, means for sending a test current over the line wire, means for connecting the set to other line wires of the signaling system so'that a lineman may use the set for communication with the wire chief at the central ofiice and a filter in the test set designed to to the line wires of-a'carrier out of? at about 2000 cycles to prevent interference by the set with a carrier system when for communicating over other lines with the central office comprising means for connecting the test set to a line for testing, means for connecting the set to other lines for communicating with the central ofiice, means for receiving and sending test pulsations over the test line and a filter to prevent unbalance by the test set of the repeaters on the line used for communication.

8. A linemans test set including means ior connecting the test set to a line wire of a signaling system for testing the condition of the line wire, means for connecting the test, set to other line wires of a signaling system so that communication may be had between the lineman and an attendant at the, central ofiic v and a filter in the test set designed to cut off at about 2000 cycles to prevent any current from the linemans transmitter hav ing components in the range of a carrier from reaching the line to avoid the linemans conversation interfering with the car-rier conversation should the lineman connect the set to the line wires of; a carrier system.

9. A linemans test set including means for connecting the test set to a line wire of a signaling system for testing the condition of the line wire, means for connecting the test set to other line wires of a signaling 5 stem so that communication may be had etween the lineman and an attendant at the central ofiice and a filter in the testset designed to cut oil? at about 2000' cycles to prevent any currents from the linemans transmitter having components above 2000 cycles from reaching the line to prevent the linemans conversation interfering with the carrier conversation should the lineman connect the set to the line wires of a carrier system-t In testimony whereof I have signed my name to this specification this 31st day of ugust, 1931..

EGINHARD DIETZE.

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