Patent GB-409026-A (GB)
Title: Improved switching arrangements for electrical signalling systems
IPC: H04L5/18
Filed: 1932-10-26
Abstract: 409,026. Controlling telegraph traffic. ELECTRICAL RESEARCH PRODUCTS, Inc., 195, Broadway, New York, U.S.A.-(Assignees of Burton, E. T. ; 97, Cypress Street, Millburn, New Jersey, U.S.A.) Oct. 26, 1932, No. 29969. Convention date, Dec. 23, 1931. [Class 40 (iii).] Reversing-switches for controlling the direction of simplex cable traffic are operated, at repeater and receiving-terminal stations, by the cessation of traffic. The drawing shows the reversing-switches S1, S2, S3 set for traffic from terminal W through repeater IR to terminal E. The transmitter T at W sends through cable C1, receiving network NWI, amplifiers AI4, AI5, cable C2, receiving network NE, amplifiers AE2, AE3, to receiver R at E. The reversing- switch S3 is held de-energized during the receipt of signals, the grid of valve 301 which controls relay 304 being negativized by A.C. signal-components received through transformer 310 and grid condenser 302. When, however, signals cease to arrive for so long that the grid charge leaks away, relay 304 pulls up, extinguishing the advisory lamp 312, energizing the reversing-switch S3 so as to cut out the receiver at 34 and cut in the transmitter at 33 ; and momentarily energizing relay 320 so as to short-circuit the amplifier AE2 and prevent it from being overloaded by the switching-operation. The time constants are so arranged that the short-circuiting magnet 320 acts before the contacts of switch S3 have been disturbed. At the repeater station IR, cessation of the signals received from W sets switch S2 for east-west instead of west-east traffic. The action is similar to that at the terminal E, but the receiving amplifier AI4 and sending-on amplifier AI5 serve for both directions of traffic. When relay 204 plills up on cessation of traffic, a transient impulse passes via condenser 221 through one or other of the windings of relay 225, according as contact 22 of switch S2 is set for east-west or for west-east traffic : thus the position of the switch is in each case altered from that appropriate to the previous direction of the traffic. The two-winding relay 225 may be replaced by a polarized relay with appropriate connections. The station W at the sending end sends out synchronizing signals in the intervals between messages, and thus holds switches S2, S3, in the position shown until a change of direction is desired. A manual or automatic time switch 106 negativizes the grid of valve 101, de-energizing relay 104, cutting in the warning lamp 112 and allowing switch S1 to reverse, the time constants being such that relay 120 maintains a short-circuit on amplifier AW2 until the switching-operation has been completed. The functions of stations E and Ware thus interchanged, and the next reversal takes place at station E in response to switch 306, and at stations IR, W in response to the cessation of east-west signals. The A.C. signal-components which control the traffic are derived from stages in the amplifying-systems such as AE2, AE3 after the earth-currents have been filtered out, so that these do not affect the control.