| 摘要 |
<P>PROBLEM TO BE SOLVED: To easily confirm the connection state of a transmission line and the communication states of respective devices during construction and maintenance. <P>SOLUTION: Interphone device is provided with a main device 1 which performs switching control over telephone calls and terminal devices 2a, 2b,... for making telephone calls through the main device via the transmission line L1 and indicators 14 and 29 for monitoring at least one of the connection state of the transmission line and communication states in real time are connected to multiplex transmission circuits 11 and 21 of the main device and terminals. As the indicators 14 and 29, synchronizing signal detecting circuits 15 and 30 which detect synchronizing signals as a physical layer and protocol analyzing circuits 16 and 31 which analyze a communication protocol as a data link layer when signals sent through the transmission line are digital signals are used. <P>COPYRIGHT: (C)2003,JPO |
