US2010644A

US2010644A - Signal transmission line

Info

Publication number: US2010644A
Application number: US686354A
Authority: US
Inventors: Albert R Rienstra
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1933-08-23
Filing date: 1933-08-23
Publication date: 1935-08-06
Anticipated expiration: 1952-08-06

Description

1935- I A. R. RIENSTRA 2,010,644

SIGNAL 'l'RAIISM]:SSIONv LINE Filed Aug. 25, 1935 INVENTOR. ARR/ENSTRA ATTORNEY r a geometric progression to four decibels.

Patented Aug. 6, 1935 UNITED STATES PATENT OFFICE SIGNAL TRANSMISSION LINE Application August 23, 1933, Serial No. 686,354

17 Claims;

, control circuits at a repeater station on a transmission line with a plurality of pairs of relays controlled according to the energy level of the signals on the line that shall effect functions in number according to a geometric ratio in controlling attenuation pads to govern the gain at the repeater station.

A further object of the invention is to provide a repeater station on a transmission line with a number of attenuation pads increasing in attennation-in a geometric progression and a number of pads having equal attenuation and with a plurality of pairs of control relays that shall efiect functions in number according to a geometric ratio in controlling the attenuation pads to govern the gain at the repeater station.

In the transmission of signals over a transmission line changes in the attenuation of the transmitting medium are caused by changes in different conditions as, for example, changes in the weather. In order to obtain good transmission of the signals, correction must be made for the changes in attenuation of the transmitting medium so as to maintain the transmission -equiv-.

alent of the line substantially constant.

In accordance with the present invention all or a number of the repeater stations on a trans mission line are provided with attenuation pads for controlling the gain. The attenuation of a number of the pads at each repeater station in.

creases in accordance with a geometric progression and a number of thepads have equal attenuation. In the circuits employed for describing the invention, eight attenuation pads are provided. The attenuation of the first five pads increases from a quarter decibel attenuation by Each of the last three attenuation pads have an attenuation of four decibels.

The attenuation pads are directly controlled by a series of pad relays, one relay beingprovided for controlling each attenuation pad. The circuits for operating the pad relays are partially completed by means of a plurality of pairs or control relays. The control relays are operated in accordance with the energy levelof the signals or a pilot current on the transmission line. The

operating circuits for the pad relays are completed by means of a time relay which is energized and operated at regular intervals.

The pairs of control relays are arranged to effect functions in number according to a geometric ratio. Moreoventhe relays in each pair operate and release in a fixed sequence. A high level relay and a low level relay which are oper ated in accordance with the energy level of the currents on the transmission line are provided for governing the operation of the control relays. For each operation of the high level relay or the low level relay the first pair of control relays is either operated or released. For every other operation of the high level relay or the low level relay the second pair of control relays is either operated or released. The remaining control relays operate in a like manner. The high level relay and the low level relay may be controlled by a pilot current on the transmission line or 2 may be controlled by the signal currents. The signal currents'may be within the voice frequency range or may be carrier currents having a much higher frequency range.

If all the attenuation pads are out of the transmission line and the energy level of the signals on the line is above normal, the high level relay is operated for effecting operation of the first pair of control relays. The first pair of control relays prepares a circuit for operating the first 0 pad relay. The circuit for operating the first pad relay is completed by the timing relay for inserting the quarter decibel pad in the line. If the energy level of the signals on the line is not corrected by the first pad the high level relay is again operated and the second one half decibel pad is inserted in the line and the quarter decibel pad taken out of the line. Such operation of the control circuits continues until the correct attenuation is inserted in the line. I! the energy level 49 of the signals on the line fallsbelow normal, the low level relay is operated for withdrawing impedance from the line by quarter decibel steps.

If the attenuation range of the pads is insufficient to correct the energy level of the signals, an alarm is sounded.

The single figure in the accompanying draw-' ing is a diagrammatic view of control circuits located at a repeater or terminal station and constructed in accordance with the invention.

Referring to the drawing a repeater station on a transmission line comprising conductors l and 2 is provided with attenuation pads A1, A2, A3; A4, A5, A6, A7 and A8. The pads A1 to A5, inclusive, in crease in attenuation according to a geometric progression. Pad A1 has one quarter decibel attenuation and the pad As has four decibels attenuation. The pads A6, A7 and As each have four decibels impedance. A plurality of pad relays L1, L2, L3, L4, L5, L6, L7 and L3 are provided for inserting and excluding the attenuation pads in and from the line circuit. The pad relay L1 is provided with armatures 3, t and 5. The relay L2 is provided with. armatures 5, l and 8. The relay L3 is provided with armatures 9, iii and H. The relay L4 is provided with armatures i2, IS and it. The relay L5 is provided with armatures i5, l5 and ii. The relay L6 is provided with armatures i 8, i9 and 28. The relay L1 is provided with armatures 2i, 22 and 23. The relay L3 is provided with

armatures

24, 25 and 26.

A plurality of pairs of control relays Z1 to Z7, inclusive, and W1 to W1 inclusive, are provided for governing the operation of the pad relays L1 to L3, inclusive, to control the attenuation in the line circuit at the repeater station. The control relays are governed in accordance with the energy level of a pilot current at the repeater sta-v tion.

v The pairs of control relays effect functions in number according to a geometric ratio. The term function as used in the specification isintended to cover the operating or the releasing of a relay. The-pair of relays comprising relays Z1 and W1 operate cr release every time a change is made in the arrangement of attenuation pads. The second pair of control relays comprising the relays Z2 and W2 either operate or release every other time a change is made in the arrangement of attenuation pads. The third set of control relays comprising the relays Z3 and W3 function every fourth time. a change is made in the arrangement of attenuation pads. The remaining pairs or control relays operate in a like manner according to the geometric ratio. It is understood inserted in the line or continuously withdrawn from the line and not inserted and withdrawn armatures 30, Si, 32 and 33. A movable contact member Stis controlled by the armature 3| of the relay W1. The relay Z2 is provided with armatures 35, st and 37. The relay W2 is provided witharmaturestt, 39, ii) and 4!. A movable switch member Q2 is controlled by the armature 39 of the relay 42; The relay Z3 is provided with armatures 3 54 and 55. The relay W3 is provided witharmatures 36,6 1, 48 and 3. A movable-switch memberfiil is controlled by the arma-' ture 4i and the relay W3. The relay Z is provided witlrarmatures Si, 52 and 53. The relay W4 is provided with armatures 5 5, 55, 56 and 5''. Amovable switch member 58 is controlledby the armature of the relay W4. The relay Z5 is provided with armatures 59, Bil and 6 l The relay W5 2 is provided with armatures 62, 63, 64 and 65. A movable switch member 86 is controlled by the armature 53 of a relay W5. The relay Z6 is provided with armatures 61, $8, 69 and. iii. The relay We is provided with armatures 713, it and :1 :5. A movable switch member '55 is controlled. by

The pairs of control relays are governed in accordance with the operation of a galvanometer 83 which is connected to the line conductors l and 2 by means of a filter 8: 1 and a rectifier 89. The filter B l is selective of the pilot current employed for controlling the gain at the repeater stations. The galvanometer 83 operates a pointer 85 above high contact members H and low contact members L.- If the energy level of the pilot current on the line is above normal, the galvanometer arm 85 will be over the contact members H and if the energy level of the pilot current on the line is below normal, the arm 85 of the galvanometer will be positioned above the contact members L. A constant speed motor 8% of any suitable type has two cam members 8'2 and 88 mounted on the armature shaft thereof. The cam member 8? closes timing contacts T at regular intervals. The cam member 88 engages a lever 98 having an arc-shaped portion Sta positioned above the arm 85 of the galvanometer 83. The lever S13 is pivotally mounted so that each time the cam member 88 is operated the arc shaped portion 9 ia thereof is moved downwardly and engages the arm 85 of the galvanometer 83. When the arm 85 of the galvanometer 83 is moved downwardly, contacts H or contacts L are closed if the arm is positioned above either of said contacts. The cam members 8'! and 88 are so positioned on the armature shaft of the motor 86 that the contact members T are-never closed at the same time the contact members H or the contact members L are closed.

The T contacts when operated by the cam member 81 complete a circuit from battery 92 for energizing the time relay 9 i. The time relay 9| is provided with an armature 93 which controls a movable grounded contact member 96. The time relay 9! serves to complete circuits partially completed by the control relays for operating the pad relays. 1 r

The low level contact members L when closed with a relay 95 operated complete a circuit from a battery 96 for operating a loW level relay 9?, If the relay 95 is released when the low level contacts L are closed, a circuit is completed for operating an alarm 99. The relay 95 is energized from a battery 99 whenever any of the W relays are operated. The low level relay 97 is provided with an armature lflt.

The high level contact members H when closed with a relay it! operated complete a circuit from battery ear 'for operating the high level relay The high level relay m3 is provided with an armature i i. If the contacts H are closed when the relay MM is released, a circuit is completed for operating the alarm 23. The relay to! is energized from a battery 5% whenever any of the W relays are in released position. Assuming all pads A1 to A3, inclusive, to be on of the line,all relays to be deenergized except the relay it! which is operated whenever a W relay is released and the H contacts to be closed by the galvanometer 83 and the cam member 88, a circuit is completed from the battery 602- turn to the armature 594. The relay W1 is operated and the armature 3i completes a circuit from the battery 01 for holding the relay W1 in operative position. The armature 39 of the relay W1 completes a circuit from battery $9 for operating the relay 95. The relay 95 is operated at this time so that the low level relay 01 may be operated at any time the L contacts are closed for reducing the attenuation in the line.

q'lhe Z1 relay is not operated at the same time 535 as. the W1 relay because both terminals of the coil of the Z1 relay are grounded. When the cam member 08 operates the lever 90 for opening the H contacts the circuit energizing the high level relay I03, is opened. Relay. I03 is released 10; and the ground applied to the right terminal of the Z1 relay is removed. The Z1 relayis then operated by a circuit extending from ground through the armature 3 I, switch member 34, coil of the relay Z1, battery C1 and ground return to The armaturefl of the Z1 rethe armature 3|.

lay prepares a circuit from battery B1 for operating the L1 relay. The armatures 28 and 29 of the Z1 relay complete no circuits at this time. The

time contacts T are then closed by the operation -15 of the cam member 81. The closing of the contact members T completes a circuit from the battery 92 for operating the time'relay 9|. The time relay 9| completes a circuit for operating the L1 relay to insert the pad A1 in the line. The

circuit completed by the time relay 9| extends from grounded battery B1 through a coil of the L1 relay, armature 21 of the Z1 relay, armature 93 ofv the time relay, contact member 94 and ground return to the battery B1. The armature 3 3 of the L1 relay completes a holding circuit from the battery B1 for the L relay when-the time relay 9| is released. 1 The

armatures

4 and 5 of the L1 relay insert the quarter decibel pad A1 in the line circuit.

I04. The W1 relay releases and completes a circuit for operating the W2 relay. The circuit for operat ing the W2 relay may be traced from the armature I04 through armature 32 of relay W1, armature 29 of, relay Z1, contact member 42, coil of the relay W2, battery C2, and ground return to the armature I04. The relay Z2 does not operate at this time inasmuch as both terminals of the coil thereof are connected to ground. Upon release 5 11,; of theI 03 relay when the H contacts are opened, the relay Z2 is operated by a circuit extending from the battery C2 through the coil of the Z2 relay, contact member 42, armature 39 of the W2 relay and ground return to the battery C2. At this c. time a holding circuit for the W2relay extends from the battery C2 through the coil ofthe W2 relay, contact member 42, armature 39 and ground return to the battery C2. When therelay I03 is released, Z1 relay is released because ground is removed from the terminal of the operating coil therefor. The release of the Z1 relay insures the release of the L1 relay when the timerelay 9| is next operated. When the L1 relay is released the quarter decibel pad A1 is removed from the line.

The operation of the Z2 control relay prepares a circuit from battery B2 for operating the L2 relay to insert the one half decibel pad A2 in the line. The operation of the time relay! I by the T contacts opens the circuit of the L1 relay and com- ?:J'pletes a circuit for operating the L2 relay. The circuit completed by the armature 93 of the time relay 9| extends from the battery B2 through a Y coil of the L2 relay, armature 35 of the Z2 relay, armature 93 of the time relay 9|, switch member :3 and ground return to, the battery B2. The re.-

If the energy level of the signals on the line is lay L2 when operated inserts the half decibel pad A2 in the line. The release of the relay L1 removes the half decibel pad A1 from the line so that the attenuation in the line has been increased by one quarter decibel.

Assuming the energy level of the line to fall below normalwhen the relays Z2, W2 and L2 are operated and the one half decibel pad A2 is in the line, then the L contacts are closed for reducing the attenuation in the line. The closure of the L contacts completes a circuit from the battery 98 for operating the low level relay 9?. The armature I00 of the relay 91 completes a. circuit from the battery C1 for operating the W1 relay. The circuit for operating the W1 relay extends from the battery'Ci through the coil of the W1 relay, switch member 34, armature I00 of the relay 9! and ground return to the battery C1. The Z1 relay is notoperated at this time because ground is connected to both terminals of the energizing coil thereof. The-armature 33 of the W1 relay completes a circuit for applying ground to the right terminal of the W2 relay which releases. The release of the W2 relay does not open the holding circuit for the Z2 relay. The holding circuit for the Z2 relay is opened upon release of the relay 9?. The Z1 relay is operated upon release of the relay 91. The relay 91 is released by separation of the L contact members.

The operation of the Z1 relay prepares a circuit by operation of the armature 21 for operating the L1 relay. The next operation of the time relay 9| by the time contacts T opens the holding circuit for the relay L2 which releases and completes an operating circuit for the L1 relay. The L1 relay upon operation inserts a quarter decibel pad A1 in the line and the L2 relay when released with draws the half decibel pad from the line. Thus, the attenuation of the line has been reduced by a quarter decibel step.

Assuming the Z2 relay and the W2 relay to be operated'and the half decibel pad A2 to be in the line and the H contact members to be closed by reason of the energy level on the line being above normal, the high level relay IDS is operated. The operation of the relay I03 operates the W1 relay, the Z1 relay and the L1 relay in the same manner as described when assumption was made that no pads were in the line and the H contacts were closed. When the Z1 relay and W1 relay are operated'and the time relay 9| is operated by the T contacts, then a circuit is completed for operating the L1 relay which inserts the quarter decibel pad A1 in the line. At this time the Z2, W2 and L2 relays are operated and the half decibel pad A2 is in the line. 1 Assuming the Z1, W1, Z2, W2, L1 and L2 relays to be operated and the energy level on the line to be above normal so that the H contacts are again closed, the high level relay I03 is operated. The armature I04 01? the relay I03 applies ground to the right terminal of the energizing coil of theW1 relay which releases. The release of the W1 relay applies ground from the armature I04 of the relay I03 through armature 32 of the relay W1, armature 29 of the relay Z1 and armature 36 of the relay Z2 to the upper terminal of the relay W2. The relay W2 then releases. The release of the relay W2 completes a circuit from the armature I04 through the armature 40 of the relay W2, armature 31 of the relay Z2, contact member 50, the coil of the W3 relay, battery C3 and ground return to the armature 04. The relay W: is operated. The relay Z3 is not operated at this time because both terminals of the coil thereof are connected to ground. ,When the relay W3 is deenergized by separation of the H 7 contacts, the Z1 and the Z2 relays are released by breaking of the circuits from batteries C1 and C2, through the operating coils of the Z1 and Z2 relays. The Z3 relay is'energized at this time by a circuit extending from the battery C3 through the operating coil for the relay Z3, contact member 50, armature ll and ground return to the battery C3. The armature A3 of the Z3 relay prepares a circuit from the battery B3 to operate the L3 relay. The circuit for operating the L3 relay is completed by the time relay 9! when the T contacts are closed. The circuit for operating the L3 relay extends from the battery B3 through coil of the L3 relay, armature 43, armature 93, contact member 9t and ground return to the battery B3. Ther one decibel pad A3 is inserted in the line upon operation of the L3 relay. The time relay 8i not only operates the L3 relay for inserting the A3 pad in the line, but also releases the L1 and L2 relays for Withdrawing the A1 and A2 pads from the line.

If the energy level of the signals on the line is still above normal value with the A3 pad in the vline and the Z3 and W3 relays operated, the H contacts are again closed for operating the high level relay l The relay N13 when'operated under the above conditions effects operation of the Z1 and W1 relays in the manner above set forth. The Z1 relay when operated prepares a circuit for operating the L1 relay which is operated upon operation of the time relay 9! by the time contacts T. The L1 relay inserts the A1 pad in the line with the A3 pad.

If the H contacts are again closed at this time the relay m3 is operated for efiecting operation of the Z2 relay and the W2 relay and the release of the Z1 relay and the W1 relay. The Z2 relay prepares a circuit for operating the L2 relay so that upon operation of the time relay 9| by the T contacts, the L2 relay is operated and the L1 relay is released. The operation of the L2 relay adds the A2 pad in circuit with the A3 pad and the release of the L1 relay withdraws the A1 pad from the line. The A2 and the A3 pads in the line have an attenuation of one and one half decibels.

If the H contacts are again closed by reason 01 the energy level of the signals on the line being above normal, the high level relay N33 is again operated for efifecting operation of the Z1 and the W1 relays in the manner above set forth. The Z2, W2 and the Z3 and the W3 relays as well as the L2 and L3 relays are held in an operated position at this time. The Z1 relay prepares a circuit for operating the L1 relay. The time relay 9i operated by the T contacts completes the operating circuit for the L1 relay for operating the L1 relay to insert the A1 pad in the line. At this time the A1. A2 and A3 pads are on the "line so that the attenuation of the pads in the lineis one and three-quarters decibels. V I

If the H contacts are again closedby reason of the high energy level of the line, the high level relay the is operated. The armature of the high level relay G3 places aground upon the upper terminal of the relay W1 so that the relay W1 releases. pletes a ground circuit for the right, terminal of the W2 relay which extends from the armature its through the armature 32, armature 29 and armature 3 5 to the right terminal of the relay W2.

The W2 relay upon releasing connects a ground.

circuit to'the right terminal of thecoil for the W3 relay. The circuit connecting ground with the right terminal of the W3 relay extends from The release of theW1 relay comthe grounded armature 104 through armature 40 of the relay W2, armature 31 of the relay Z2 and armature M of the relay Z3 to the right terminal of the coil of the W3 relay. The relay W3 upon releasing completes a circuit for operating the W4 relay. The circuit for operating the W4 relay extends from battery C4 through the coil of the W4 relay, contact member 58, armature 45 of the Z3 relay, armature 48 of the W3 relay, armature I84 of the H33 relay and ground return to the battery C4. The W4 relay upon operation establishes a holding circuit for itself through the armature 55. The Z4 relay is not operated atthis time because both terminals of the energizing coil thereof are connected to ground; When the high levelrelay 5% is released by separation of the contact members H, the Z4 relay is operated from the battery C4 through the armature 55 of the W4 relay. At the same time the Z1, Z2 and Z3 relays are released. The Z4 relay prepares a circuit for operation of the L4 relay. Upon operation of the time relay 9i the L4 relay is operated by a circuit extending from the battery B4 through the coil of the L4 relay, armature 5|, armature 93, contact member t4 and ground return to battery B4. The operation of the L4 inserts the two decibels pad A4 in the line. At the same time the operation of the time relay 9! releases the L1, L2 and L3 relays to withdraw the A1, A2 and A3 pads from the line.

If the H contacts are again closed the Z1, W1 andL1 relays are operated for inserting the quarter decibelpad A1 in the line. If the H contacts are again closed the Z2 and W2 relays are operated to insert the half decibel A2 pad in the line while the Z1, W1 and L1 relays are released to withdraw the quarter decibel pad A1 from the line. The next operation of the H contacts serves to operate the Z1, W1 and L1 relays to insert the quarter decibel pad A1 in circuit with the A2 and A4 pads. The next operation of the H contacts operates the Z3, W3 and L3 relays to insert the one decibel pad A3 in circuit with the two decibel pad A4, at the same time the relays Z1, W1, Z2, W2, L1 and L2 are released to withdraw the A1 and A2 pads from the line.

With the pads A3 and A4 in the line producing three decibel attenuation and the relays L3, L4, Z3, W3, Z4 and W4 operated, the contacts H are again closed if the energy level on the line is above normal. The high level relay I03 is operated to insert the quarter decibel pad A1 in the line. The next operation of the high level relay 103 by the H contacts inserts the half decibel pad A2 in the line and withdraws the quarter decibel pad A1. The next operation of the high level relay I63 by the H contact inserts the quarter decibel pad A1 in the line. At this time the pads A1, A2, A3 and A4 are in the line producing three and three-quarter decibel attenuation.

'If the high level relay m3 is again operated by the H contacts, the circuit grounded by the armature I84 of the relay Hi3 places ground on the right terminal of the coil for the W1 relay. The W1 relay releases. The armature 32 of the W1 relay then effects release of the W2 relay. The armature MB of the W2 relay then effects release of the W3 relay. The W3 relay by means of its armature 48 effects release of the W4 relay. Upon release of the W4 relay a circuit is completed through the armature 56 for efiecting operation of the W5 relay. The W5 relay upon operation completes a holding circuit from the battery C5 through the armature 63.

The Z5 relay is not operated at this time inasmuch as a grounded circuit is connected to eachterminal of the coil of. the relay. Upon release of the I03 relay by separation .of the H contacts the relays Z1, Z2,

Z3 and Z4 arereleased and the Z5 relay is operated. The operation of the Z5 relay prepares a circuit from the battery B5, through the armature 59 for operating. the L5 relay upon the next operation 01" the time relay 9!. The operation of the time relay 9! by the T contacts releases the L1 relay, the L2relay, the L3 relay and the L4 relay to withdraw the pads A1, A1, A3 and A4 from the line. The relay L5 is operated to" insert the pad A5 in the line.

The pad A5 inserts an attenuation of four decibels in the line. The relays L5, Z5 and W5 are operated at this time. The next'operation of the H contacts effects operation of the Z1, W1 and L1 relays to insert the A1 pad in circuit with the A5 pad. If the H contacts are again operated by reason of high energy level on the line, the Z2, W2 and L2 relays operate to insert the A2 pad in the line and the Z1, W1 and L1 relays release to withdraw the A1 pad from the line. The next operation of the H contacts efiects operation of the Z1, W1 and L1 relays to insert the A1 pad in circuit with the A2 and A5 pads. At this time four and three-quarter decibels impedance is in theline. The next closureof the H contacts effect operation of the Z3, W3 and L3 relays to insert the A3 pad in the line and the release of theZ1, W1, L1, Z2, W2 and L2 relays to withdraw the A1 and the A2 pads from the line. The next closure of the H contactseffects operation of the Z1, W1 and L1 relays to insert the A1 pad in the line. The next closureof the H contacts efiect's operation of the L2, Z2 and W2 relays to insert the A2 pad in the line and release of the Z1, W1 and L1 relays to Withdraw the A1 pad from the line. The next operation of the H contacts 0 erates the Z1, W1 and L1 relays to insert the A1 pad in circuit with the A2,'A'5 and A5 pads. The next closure of the H contacts effects operation of the Z4, W4'and L4 relays to insert the A4 pad in the line and the release of the Z1, W1, L1, Z2, W2, L2, Z3, W3 and L3 relays to withdraw the A1, A2 and A3 pads from the line.

The next closure of the H contacts effects operation of the Z1, W1 and L1 relays toinsertthe A1 pads in the line. The next closure of the H contacts operates the Z2, W2 and L2 relays to insert the A2 pad in the line and the release of the Z1, W1 and L1 relays to withdraw the A1 pad from the line. The next closure of the H contacts operates the L1, W1 and Z1 relays to insert the A1 pad in the line. The next closure of the H contacts operates the Z3, W3 and L3 relays to insert the A: pad in the line and the release of the Z1, ,W1, L1, Z2, W2 and L2 relays to withdraw the A1 and the A2 pads from the line. The next closure of the H contacts operates the Z 1, W1 and the L1 relays to insert the A1'pad in the line. The next closure of the H contacts operates the Z2, W2 and'L2 relays to insert the A2 pad in the line to produce an impedance of seven and threequarters decibels;

1 lease the W1 relay. The armature 32 of the W1 relayeffects release of the W2 relay. The arma ture 40 or the W2 effects the release of the W3 relay. The armature 48 of the W3 relay ef fects release of the W4 relay. The armature 56 ofthe W4 relay effects release of the W5-relayi Upon release of the W5 relay, the armature 64 completes a circuit for'operating the W6 relay from the battery 66. The circuit .for operating the W6 relay may be traced from the battery 0'6 through the coil of the W6 relay, contact member it, armature 6! of the Z5 relay, armature 84 of The Z6 relay is operated by.circuit from battery C6 through the coil of the relay, contact members i 6, armature 13' of the W6 relay and ground return to the battery C6. Upon operation of the .relay 3!, the L1, L2, L2 and L4 relays are released to withdraw the pads A1, A2, A3 and A4 from the line. The'Ls relay is maintained operated and a circuit is completed for operating the L5 relay. The L5 relay maintains the A5 pad in theline and the L6 relay inserts the A5 pad in the line so that the attenuation in the line is'now eight decibels. The circuit for operating the L5 relay. extends from the battery B5 through a, coil of theiiLs relay, armature 3'! of the Z6 relay, armature 9310f inclusive, and relays W1 to;W4, inclusive, to insert the A1 to A4 pads in the linewith, the A -and A6 pads. With the A1 130,116 pads in the line, the impedance is eleven and tlneefluarters decibels. The next operation of the H contacts in the customary manner releases the W1 relay which releases the W2 relay, the W2 relay releases the W relay, and the W3 relay releases the W4relay. Thearmature 56'of the W4 relay oompletesa circuit for operating the W5 relay. The circuit completed for -operating the W5 relay extendsfrom the battery C5 through the coil of thews relay, a contact member 66, armature 53 of the Z4 relay, armature 55 of the W4 relay, armature we of the M3 relay and ground return to the battery C5. The W5 relay is operated but the Z5 relayis not operated until the release of. the l03.relay. The release of the sea relay effects releaseiof the Z1, Z2, Zgand Z4 relays. The Z5 relay prepares a circuit for operating the L2 relay. Upon operation of the relay 9 I, by the time contacts T, the relays L1, L2, L3 and L4 are released to withdraw the pads A1, A2, A3 and A4 from the line; The L5,; and L6 relays are held in operated position by reason. of the Z6 being held operated. The L7 relay, is operated by. a circuit extending from the battery B7, armature iii of the relay Z6, armature 59 of the relay Z5, armature -93 ofthe time relaylil; contact member Stand ground return to the ba tery B7. At this time the relays L5, L6 and L2 are operated to insert the A A6 and A2 pads in-the line. The pads A5, A6 and A 1 have an=attenuation of 12 decibels. I V V I v If the H contacts are operated continuously by reason of high energy level on the line with the A5, A6 and A7 pads in the line, the A1, A2, A3 and A4 pads will be inserted in the line by one quarter decibel steps as disclosed heretofore. ,When the A1 to A7 pads are inserted in the line, the L1 to L7 relays are operated, the Z1 to Z6 relays are operated and the W1 to We relays are operated. With the circuits in such condition the next operation of the H contacts energizes the H13 relay to release the W1 relay, the W1 relay releases the W2 relay, the W2 relay releases the W3 relay, the W: relay releases the W4 relay, the W4 relay releases the W5 relay and the W5 relay releases the We relay. The armature M of the We relay completes a circuit for operating the W7 relay. The circuit for operating the W7 relay extends from the battery. 07 through the coil of the W7 relay, cont-act member 8|, armature E9 of the Z6 relay, armature M of the We relay, armature M of the H33 relay and ground return to the battery C7. The Z7 relay is not operated at this time by reason of both terminals of the coil thereof being grounded. The release of the relay I93 efiects release of the Z1, Z2, Z3, Z4, Z5 and Z6 relays and effects operation of the Z7 relay. The circuit for operating the Z7 relay extends from the battery C7 through the coil of the Z7 relay, contact member 8|, armature 88 of the W7 relay and ground return to the battery C7. Operation of the time relay 9| by the T contacts efiects release of the L1, L2, L3 and L4 relays. The L5, L6, L7 and L8 relays are held operated by the circuits completed by the Z7 relay. The circuit for operating the L5 relay may be traced from the battery B5 through the coil of the L5 relay, contact member closed by the armature 18 of the Z7 relay, armature 93 of the time relay 9|, contact member 94 and ground return to the battery B5. The circuit for operating the Le'relay may be traced from the battery Bs through a coil of the relay Ls, armature 'll of the Z7 relay, armature 93 of the time relay 9|, contact member 94 and ground return to the battery B6. The circuit for operating the L7 relay may be traced from the battery B7 through the coil of the relay L7 armature ll of Z7 relay, armature 93 of the time relay 9|, contact member 94 and ground return to the battery B7. The circuit for operating the L8 relay may be traced from the battery Ba through the armature 18 of the Z7 relay, armature 93 of the time relay 9|, contact member Q4 and ground return to the battery B3.

The operation of the L5, L6, L7 and La relays inserts the pads A5, A6, A7 and A8 in the line to produce an attenuation of sixteen decibels. It is apparent at this time that if so desired, the pads A1, A2, A3 and A4 may be inserted in the line with the pads A5, A6, A7 and A3 to produce a nineteen and three-quarter decibel attenuation. If all the pads A1 to As, inclusive, are in the line and the H contacts are closed a circuit is completed for operating the alarm 88. The attenuation is withdrawn from the line under the control of the L contacts by one quarter decibel steps in the same manner as the attenuation is added to modifications are intended to be covered by appended claims.

' What is claimed is:

1. In combination, a plurality of pairs of control relays for controlling the gain at a station on a transmission line, means for insuring the operation of the relays by pairs with the operation of the relays of each pair in a predetermined sequence and for insuring the release of the relays by pairs with the release of the relays of each pair in the same sequence, a pair of high level contact members, and means comprising circuits governed by said contact members for controlling said pairs of relays to effect functions the number of Which correspond to a geometric progression.

2. In combination, a transmission line having a station, a plurality of attenuation pads adapted to be inserted in the line for controlling the gain at the station, a number of said pads increasing in attenuation according to a geometric progression and a number of said pads having equal attenuations, and means operated according to the energy level of the signals on the line for controlling said pads to change the attenuation at the station by equal attenuation steps.

3. In a signal transmission system, a transmission line, a plurality of attenuation pads adapted to be inserted in the line for controlling the attenuation, a number of said pads increasing in attenuation in a geometric progression and a' number of said pads having equal attenuations and means comprising a plurality of sets of relays efiecting functions the number of which correspond toa geometric ratio for inserting said pads in the line by equal attenuation steps.

4. In combination, a transmission line having a station thereon, a plurality of attenuation pads for controlling the attenuation. at the station, a number of said pads increasing in attenuation in a geometric progression and the remaining pads having equal attenuations, a pad relay for controlling each pad, pairs of control relays for governing said pad relays, and means controlled according to the energy level of a pilot current on the line for operating said control relays to govern the operation of said pad relays and adjust the attenuation in the line at the station by equal attenuation steps.

5. In combination, a plurality of attenuation pads for controlling the attenuation on a transmission line, a number of said' pads increasing in attenuation in a geometric progression and the remaining pads having equal attenuations, a pad relay for controlling the operation of each of said pads, pairs of control relays controlling the operation of the pad relays, means for governing said control relays according to the energy level of a pilot current on said line to prepare circuits for operating said pad relays, said control relays effecting functions the number of which correspond to a geometric progression when the attenuation is changed by a number of steps in one direction, and means operated at regular time intervals for effecting operation of the pad relays selected by saidcontrol relays.

6; In combination, a transmission line, a plurality of attenuation pads for controlling the attenuation on the line, a pad'relay for controlling each of said pads to govern the attenuation on the line, pairs of control relays for partially completing circuits to operate said pad relays, means for controlling said pairs of control relays to effect functions the number of which correspondto ageometric progression, means for effecting operating and releasing of the relays of each pair of control relays in a fixed sequence,

means comprising two pairs of contactmembers for governing the control relays'according to the energy level of a pilot current on, theline and means comprising a pair of contactmembers operated at fixed intervals for completing the? pad relay circuits partially completed by the pairs of control relays. l

7. In combination, a, plurality of; attenuation pads for controlling the attenuationEcm a trans-- mission line, a pad relay associated with-each attemiation pad for controlling the insertion and withdrawal of 'the pads in and out of said line, a pluralityof pairs, of control relays for preparing circuits to'operate said pad relays, means operated at regular time intervals for effecting operation of 'the pad relays selected by said control relays, means for controlling said pairs: ofcontrol relays to effect functions thereby the number of which correspond to a geometric progression, means for effecting functioning of the relays of each pair of control relays in a fixed sequence, and means for governing'the control relays according to the energy level of a pilot current on the line.

8. In combination, a plurality of attenuation padsfor controlling the attenuation on a transmission line, a number of said pads increasing in attenuation in a geometric progression and a number of said pads having equal attenuations, a series of pad relays for controlling the insertion and withdrawal of said pads in and out of said line, a plurality of sets of control relays for preparing circuits for operating said pad relays, said control relays effecting functions the number of which correspond to a geometric ratio when operated for inserting attenuation pads in the line, means for operating said control relays according to the energy level at the repeater station of the currents on the line,-and means operated at regular time intervals for effecting operation of the pad relays selected by said control relays to change the attenuation by equal steps.

9. In combination, a plurality of attenuation pads for controlling the attenuation on a transmission line, apad relay for controlling each of said pads to govern the line attenuation, a pair of control relays for controlling the operating circuit of each of said pad relays, means for controlling the pairs of said control relays according to the energy level on the line, each operated pair of control relays partially completing a circuit for operating the associated pad relay, and

,means operated at constant intervals for com plating the circuits of thepad relays which have been partially completed by the pair of control relays.

10. In combination, a plurality of attenuation pads for controlling the attenuation on a transmission line, a pad relay for controlling each of said pads to govern the line attenuation, a plurality of pairs of control relays for controlling the operation of the pad relays, each pair of control relays when operated partially completing an energizing circuit for a pad relay, means comprising high level contact members and low level contact members for operating said pairs of control relays according to the energy level on the transmission line, and means comprising timing contact members closed at fixed intervals for completing the energizing circuits of the pad relays which have been partially completed by the pairs of control relays and for releasing any operated pad relay when the pair of control relays associated therewith has been released.

11. In combination, a transmission line, a repeatefstation on said line; a plurality of attenuation'padsfor controlling the gain at the re peate-r station, a pad relay for-controlling each of said pads,a pluralityof pairs of cc trol rclays, each of said pairs oi relays whe erated serving to partially complete-an energizing cir. cuit for a pad relay, highlevelcontact members, low level contact members, means for operating said high level contact'members when high enrgy level on said lineto control said'pa relays and for operating'saidlow le v i members when low energy level is orrsaid line to con-trol said pairs of relays, and means'comprising a pair of timing contact tin-em, s closed fixed intervals for completing the: Cirbuits pad relays which have been partially completed by the pairs of control relays. j M

12. In combination, two series of relaysdivided into pairs, each of said pairs being formed by one relay from each series of relays, a pair of contact members, and means controlled by the oper ating and releasing of said pair of contact members for controlling said series of relays so that the pairs of relays effect functions the number 1 lays, a pair of contact members, and means comprising circuits controlled by the opening and closing of said contact members for operating the first pair of relays and for operating any other selected pair of relays by controlling the pairs of relays back of said selected pair of relays so that the pairs of relays back of the selected pair of relays effect functions the number of which functions correspond to a geometric progression.

14. In combination, two series of relays divided into pairs, each of said pairs of relays being formed by one relay from each series of relays, a pair'of high contact members, a pair of low contact members, means comprising circuits controlled by said high contact members for operating the first pair of relays and for operating any other selected pair of relays by controlling the pairs of relays back of said selected pair of relays so that the pairs of relays back of the selected pair of relays effect functions the number of which functions correspond to a geometric progression and controlled by said low contact members for releasing the first pair of relays if operated alone and for releasing another pair of operated relays by controlling the pairs of relays back of the operated pair of relays so that the pairs of relays back of the operated pairs of relays effect functions the number of which functions correspond to a geometric progression.

15. In combination, a transmission line, a plurality of attenuation pads for controlling the attenuation on the transmission line, a number of said pads increasing in attenuation according to a geometric progression and a number of said pads having equal attenuations, means comprising pairs of control relays for controlling said attenuation pads to adjust the attenuation of the line by equal attenuation steps, and means for controlling said pairs of control relays to effect functions the number of which functions rality of attenuation pads for controlling the attenuation on the transmission line, a number of said pads increasing in attenuation according to a geometric progression and a number of said pads having equal attenuations, a pad relay for controlling each of said pads, a plurality of pairs of control relays for controlling the operation of said pad relays, each pair of control relays when operated partially completing an energizing circuit for a pad relay, means controlled by the energy level on said line for controlling said pairs of control relays to effect functions the number of which functions correspond to a geometric progression, and means comprising a pair of timing contact members operated at fixed intervals for completing energizing circuits for the pad relays that have been partially completed by the pairs of control relays.

7 17. In combination, a transmission line, a repeater station on said line, a plurality of attenuation pads for controlling the gain at the repeater station, pairs of control relays for controlling said attenuation pads, a pair of high level contact members, a pair of low level contact members, means for operating said high level contact members in case of high energy level on said line and for operating said low level contact members in case of low energy level on said line, and means comprising circuits controlled by the high level contact members in case of high energy level on said line and by the low level contact members in case of low energy level on said line for effecting functions by said pairs of relays the number of which functions correspond to a geometric progression.

ALBERT R. RIENSTRA.