| 摘要 |
PURPOSE:To turns on the illumination of a telephone set irrespectively of other switches related to the illumination when the hand set is off-hooked, by adding a control circuit having a simple judging logic and processing logic to the telephone set with illumination. CONSTITUTION:A control circuit 4 which is operated by the command of a hook switch 3 for off-hooking a hand set is installed to a telephone set with illumination, whose keyboard 1 is provided with a lighting circuit 2 which lights the keyboard 1 and an illumination changeover switch 31 which acts as a control means controlling the turning-on and turning-off of the lighting circuit 2. When the hand set sets the hook switch 3 to the off-hook condition by means of the control circuit 4, the lighting circuit 2 is automatically turned on and, when the brightness of the circumference around the telephone set exceeds a prescribed level just before the off-hook condition is set, the circuit 4 automatically inhibits the control for turning on the circuit 2. |
