| 摘要 |
PURPOSE:To improve reliability to keep a trunk line call by providing a switching part that connects alternatively a cross point and a dial sending part at a trunk line. CONSTITUTION:With inputting power to a system, in an input/output process followed by an initialization, a data is fetched in through a line 106 and is stored at an input buffer. A control circuit 108, based upon the data stored, prepares the lightening of LEDs or the sending process of calling tones for key telephone sets 1021-102m, and stores required output data at an output buffer, and also, prepares the sending of the data for the calling or that of dial data, etc. and stores required output data at the output buffer. At the next, the control circuit 108, in the input/output process, outputs the data stored at the output buffer through the line 106. Afterwards, the same operation is repeated.
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