| 摘要 |
1,100,716. Selective signalling systems. GENERAL ELECTRIC CO. 22 Nov., 1965 [9 Dec., 1964], No. 49474/65. Heading G4H. Various devices on a railway locomotive are selected for operation by transmitting a characteristic sequence of tone signals, the first of these being a safety tone without which none of the devices may be operated. The transmitter, Fig. 4, comprises a timing circuit 20 which first enables gate 62 to transmit the safety tone. Subsequently the timing circuit energizes in sequence two sets of manually actuated switches 75-84 which are connected to the appropriate oscillator gates 57-61. The receiver, Fig. 2 (not shown) comprises corresponding filters (34) tuned to the respective frequencies. The safety tone channel includes an output relay (STR) which closes a contact to supply power to line (51). The safety tone channel enables storage means (46) in the selection channels whereby reception of the two subsequent selection tones causes energization of the appropriate two relays (LFR), the contacts of these relays being so arranged that only the appropriate one of the devices (UD) is connected across the power supply through the closed contact of relay (STR). |
