GB468332A - Improvements in or relating to systems for the electrical transmission of signals to railway locomotives - Google Patents

Abstract

468,332. Electric signalling systems. SVENSKA AKTIEBOLAGET GASACCUMULATOR. Nov. 11, 1936, No. 30841. Convention date, Nov. 11, 1935. [Class 40 (i)] [Also in Group XXX] A signalling arrangement for railway shunting yards in which signals are transmitting from a central control point is provided at various local points in the yard with means for causing an emergency signal to be transmitted and any previously set up signal to be cancelled. For example, different audible code signals denoting " stop," " back," " forward," may be transmitted to a shunting locomotive, by means of cams 17 ... 19 periodically interrupting the modulation circuit for a wireless signalling system 1. The control tower operator transmits the signal " back " by depressing a button 44 to pick up a relay 39 which closes its contact 36 whereby a relay 24 is picked up as soon as a cam 26 closes a contact 30. The relay 24 remains up so long as a further cam 27 closes a contact 33, the stick circuit including a contact 55 of the relay 24 and the winding of a relay 42 ; a front contact 21 of the relay 24 closes a point in the modulation circuit and the cam 18 gives the " back " code form to the audible signal. The pick and stick circuits for the push button relays 38 ... 40 include front contacts 90, 74 of a relay 75. If an emergency arises any one of a number of local pushes 76 ... 78 spread about the shunting yard is depressed and remains locked down. Such action de-energizes the relay 75 which at its back contact 86 picks up the relay 23 when the cam 26 closes contact 29. The relay 23 remains energized, together with the series relay 42, so long as cam 27 closes contact 32. Front contact 20 of relay 23 closes a point in the modulation circuit and the cam 17 gives the " stop " code form to the audible signal. Further, the front contact 41 of the relay 42 energizes a vibratory relay 88 over a back contact 87 of the relay 75 ; such vibratory relay 88 gives an alternating pitch to the audible note by periodically switching out the condenser 66 so altering the periodicity of the modulating circuit. Thus the emergency operation causes an audible signal of the " stop " code form and of a special pitch character to be transmitted. Any previous signal transmission set up in the tower is connected since the pick and stick circuits of the push buttons relays 38 ... 40 are opened at the front contacts 90, 74 of the now deenergized relay 75. When a local push 76 ... 78 is depressed it can only be released by a special key. Lamps 79 ... 81 adjacent the pushes and lamps 82 ... 84 on a miniature diagram in the tower are lit to indicate the particular push operated. A checking circuit energized by the aerial current sounds a loud-speaker 11 and lights a lamp 63 in the tower.