| 摘要 |
The time switch has a monostable flip flop operating a relay (3) whose contacts (4) are in series with the load (1). A monitoring lamp (7) is connected in series with a diode (15) across the load and indicates when current is flowing through the latter. To provide a check that the lamp is working correctly, a pushbutton (11) connects it across the DC supply. If the lamp fails to light when this button is depressed, it is faulty. A transistor (12) is connected by its collector/emitter path between the flip flop's control input (13) and the lamp. Its base is connected to the diode such that this diode shunts its base/emitter junction via two resistors. |
