| 摘要 |
PURPOSE:To confirm presence/absence from an arbitrary telephone set connected to an exchange at any time and from any plate, by identifying the presence/ absence with tone specification by a specific number dialed from the telephone set. CONSTITUTION:When a central processing unit 5 receives the specific numbers X1 (presence setting) and X2 (absence setting) dialed by an extension telephone set A via a register circuit 7 and a trunk control circuit 8, a presence display memory in a main memory 6 is indexed, and the data of the presence/absence (0/1) is written based on the specific number dialed to the said bit. To confirm a presence state set in such way, the specific number X3 (a number for confirming the presence state) and the extension number of an opponent desired to confirm the presence state are dialed from an arbitrary extension telephone set B. Then, the central processing unit 5 indexes the presence display memory in the main memory 6, identifies it, and a busy tone BT is connected to the extension telephone set B when the presence is confirmed, and a service set tone SST when the absence is confirmed. Thus, it is possible to confirm the presence/absence from the arbitrary telephone set connected to the exchange.
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