Request bus stop signal lamp control circuit - uses push buttons to switch on thyristor and door switch to disconnect lamp after passengers alight

摘要

The circuit controls a lamp, signalling to the driver of a bus in suburban traffic to stop at the request stop. The lamp has a minimum light intensity to counteract the sunshine, and is dimmed at night to avoid discomfort to the driver. Passengers switch on the request stop lamp (2) from push-buttons (3), so that the voltage is applied to the control electrode of thyristor (4). The closed door switch (5) ensures firing of the thyristors and the lamp (2) lights up. The cold resistance of switched off outside lamps (6) shunts the series resistance (7) and reduces the intensity of lamp (2). Opening of the door turns off the thyristor and the lamp is then extinguished.