| 摘要 |
PURPOSE:To reduce an occasion for call disturbance and to simplify an operation with the elimination of an additional operation in a calling ST by sending a busy tone for a calling telephone set when a called telephone set is busy, starting a timer at the same time and sending an extension call signal for the called telephone set when the timer is terminated. CONSTITUTION:As a control means, a main processor CPUm 21 and a sub processor CPUs 22 are provided and the CPUs 22 performs the transmission/ receiving of a data signal between each ST with controlling a data transmission/ receiving circuit 12 and stores the operating data received by each key telephone set ST at a variable memory RAM 23 which is used in common by the CPUm 21 and also, reads out the control data to each ST stored ad the RAM 23 by the CPUm 21 and sends it to each ST. However, each of the CPUm 21 and the CPUs 22 is equipped with the RAM 23, a fixed memory ROM 24 and the same internal memory and performs a data process and when processing, a control is performed while accessing a required data at the internal memory and the RAM 25.
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