| 摘要 |
1292128 Protective arrangements COMPAGNIE INDUSTRIELLE DES TELECOMMUNICATIONS CIT-ALCATEL 19 Dec 1969 [23 Dec 1968] 62114/69 Heading H2K An arrangement for controlling the supply to an electronic apparatus S and preventing the completion of the supply circuit to the apparatus when the apparatus is short-circuited or has a low resistance fault, comprises a transistor T2 through which the load current may be supplied to the apparatus, a " control " transistor T1 which is rendered conductive by a control signal at E, a " detecting " transistor T3 which is rendered conducting by T1 only when the resistance at S is sufficiently high, and causes the transistor T2 to conduct. Should the apparatus have a low resistance, T3 is not rendered conducting so that T2 does not conduct and a capacitor C is charged from E until after a delay a Zener diode ZN breaks down. This permits discharge current to flow to the base of a " signalling " transistor T4 to cause it to conduct to provide a fault indicating signal at SN and to render the transistor T1 non- conductive. |
