| 摘要 |
1,182,234. Exchange apparatus. ERICSSON TELEPHONES Ltd. 4 Oct., 1968 [8 March, 1968], No. 11514/68. Heading H4K. A self-stepping circuit for an electromagnetic device such as a uniselector comprises a magnet coil D in series with interrupter contacts I, a resistor R, light current contacts r to initiate self-stepping, and a relay B; drive to the magnet coil D being taken from an amplifier T1, T2, T3, activated by contacts b of relay B after a delay introduced by circuit A. The current operating relay B in response to operation of contacts r is insufficient to operate magnet coil D or do harm to contacts r. The delay introduced by A allows magnet coil D to deenergize fully before being required to take another step. A diode q protects transistors T1, T2 of the amplifier from overvoltages when coil D is disconnected. Contacts d operate to drive the magnet coil D for single step operation. The contacts b, d and r may be reed contacts or may be transistor switches. |
