| 摘要 |
A switching circuit comprises a switching element, preferably a triac, connected in series with a drive coil of a switch, the switch being operable in response to a pulse of current through the drive coil, the switching element being operable to allow current to flow in either direction in response to a control pulse, the drive coil and switching element being connectable, in use, to an alternating current source, and the circuit further comprising means for supplying a control pulse to the switching element. The control pulse may be supplied by a microprocessor or RC network, and allows current to be supplied to the drive coil in either direction depending on the point in the alternating current cycle at which the control pulse is supplied. The circuit can be used with a mains supply to readily provide a pulse of current in either direction through the drive coil, of a sufficiently high level to overcome the contact force provided in the switch by a strong permanent magnet.
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