| 摘要 |
PURPOSE: A circuit and a method for indicating the state of a subscriber unit in a private exchange system are provided to drive an LED(Light Emitting Diode) connected with subscriber cards of the subscriber unit, according to the normal, abnormal and under-use state of each subscriber card, so that users can easily detect the state of the subscriber cards. CONSTITUTION: If power is applied to a subscriber unit, a controller(100) controls the subscriber unit to blink an LED(Light Emitting Diode,370) in each subscriber card(111-11n) and initializes a system. The controller(100) periodically checks the normality of the subscriber cards(111-11n). The controller(100) prevents low signals from being outputted to abnormal cards of the subscriber cards(111-11n), to continuously blink the LED(370). The controller outputs low signals to normal cards of the subscriber cards(111-11n), to turn off the LED(370). The controller(100) decides whether subscriber cards under use exist. If subscriber cards under use do not exist, the controller(100) repeats the step of outputting low signals to the normal cards. If subscriber cards under use exist, the controller(100) turns on the LED. The controller(100) decides whether the subscriber cards(111-11n) under use are normally operated. If the subscriber cards(111-11n) under user are not normally operated, the controller(100) blinks the LED(320) of the subscriber cards(111-11n).
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