| 摘要 |
PURPOSE:To effectively conduct the test of a MODEM equipment and a communication line used by each communication equipment by selecting a cyclic packet returned while being circulated on a loop type communication line so as to return it to an interface INF and using it as a local loopback test. CONSTITUTION:When a loop communication control circuit CNT receives a packet RXPACKET, a discrimination means 11 decides whether the received packet is a packet sent from other communication equipment or a cyclic packet circulated while being sent from the own station. When it is decided that the packet is sent from other communication equipment, an H level control signal RXDET is outputted to a selection circuit SEL. On the other hand, when a cyclic packet RT PACKET is received, an H level control signal RTDET is outputted to the selection circuit SEL. In such case, the selection circuit SEL brings the packet reception detection signal PDET to the H level. The interface INF receives it to receive the cyclic packet from a loop communication control circuit CN and uses it as a local loopback test.
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