| 摘要 |
The circuit has voltage converter (2) providing a supply voltage to the control unit (1). A first switching unit (T10, R10, D10) monitors the external voltage and when this exceeds a predetermined threshold level, this produces a control signal on an input (E2) of the control unit. User circuits are connected to the supply according to the status of this control input. The circuit comprises a voltage converter (2) with input and output which provides the supply voltage, after application of an external voltage. A control unit (1) is electrically connected to the supply voltage (VCC) and to earth. A first switching unit (T10, R10, D10) monitors the external voltage and when this exceeds a predetermined threshold level, this produces a control signal on an input (E2) of the control unit. A second switching unit forms a part of the control unit (1), and acts to connect one or more users (RL) to the circuit, according to the status of the input applied to the input (E2). One user circuit controlled in this way is the control unit itself, changing from a rest state to an operational state.
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