| 摘要 |
PROBLEM TO BE SOLVED: To reduce the deterioration rate in the light emitting characteristic of a light emitting element and to prevent burning by providing a timer circuit that interrupts an input signal to a drive circuit when it is received continuously for a prescribed time or longer to an input of the drive circuit. SOLUTION: An output of a control circuit 1a is given to a base input of a terminal equipment 1c via resistors 1f, 1b, a timer circuit 1d is connected to a base of the TR 1c and its output is connected to a base of an NPN TR 1e whose emitter connects to a reference voltage and whose collector connects to a connecting point of the resistors 1f, 1b. Through the constitution above, when the signal is given to the transmitter for a time shorter than a time set in advance by the timer circuit 1d, the operation similar to a conventional transmitter is conducted, and when the signal is given longer than the preset time, the TR 1e is conductive to set a base input of the TR 1c to a low level thereby preventing a large current from flowing to the light emitting element 2. |
