| 摘要 |
PURPOSE:To realize an economical MW signal transmission system by providing a loop detection circuit or the like in common without the provision of a loop detection circuit or the like at each subscriber circuit and providing a small sized circuit to each subscriber circuit thereby avoiding the size of system from being increased. CONSTITUTION:A message waiting (MW) signal sending function is provided to subscriber circuits 4-1-4-N and a loop detection circuit 51 detecting off-hook of telephone sets 2-1-2-N and the MW signal generator 52 are provided in common. An MW trip signal is sent to all subscriber circuits 4-1-4-N when the loop detection circuit 51 detects off-hook, and the subscriber circuits 4-1-4-N sending the MW signal while receiving said signal stop once the sending of the MW signal to check the hook state of the accommodated telephone sets 2-1-2-N, and when the telephone sets 2-1-2-N are in the on-hook state, the MW signal is sent again. Thus, the economical MW signal sending system is realized without increasing the size of system by adding only the small sized MW trip control circuit 42 and a relay MW to the subscriber circuits 4-1-4-N.
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