| 摘要 |
Sub-rate calls of 8kxn bps (where n=1, 2, . . . ) are multiplexed in any combination on a digital transmission path having a basic (unit) bit-rate (64 kbps) as a unit. In order to set a sub-rate call of 8kxn bps in response to a call setting request from a low-speed data terminal, if a circuit switching call of 64 kbps is already set between the switching offices and the multiplex communication can be made at a rate required by the sub-rate call, the multiplex operation is made on 64 kbps circuit switching call to set the sub-rate call between terminals. On the other hand, if the sub-rate call can not be set, a circuit switching call having a new basic bit rate (64 kbps) is set between the switching offices at a time of occurrence of the sub-rate call if necessary to set the sub-rate call between the terminals.
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