| 摘要 |
The voltage of an AC supply (fig 1, 10) for a lamp is monitored and, when the lamp is operating correctly activates an auxiliary load (fig 1, R27,R5) to draw current from the supply at preset phase intervals and of a magnitude that depends upon the supply voltage. The circuit allows low energy lamps such as light emitting diode (LED) lamps to be substituted for incandescent lamps in a traffic light without modification of signal lamp failure detection circuitry. The auxiliary load current may be drawn at phase intervals that may be adjusted to correspond with those used to monitor incandescent lamp current, is varied in response to the supply voltage which may be lowered for lamp dimming and may be tailored to emulate that of an incandescent lamp. |
