| 摘要 |
PURPOSE:To decrease the number of component parts by connecting the subscriber circuit of the general 2-wire telephone unit to the telephone reception line of the carrier circuit. CONSTITUTION:In case the signal is transmitted to the register or the trunk from the carrier circuit, relay R of the carrier additional unit via the earth of the RG2- wire is operated. And the DC loop is formed at the telephone reception line, and then the signal is transmitted in the DC loop system to be received at relay A. In case the signal is transmitted to the carrier circuit from the register or the trunk, the simplex system using the middle point of the coil provided to transmission line is applied. The circuit of the 2-wire telephone set is connected to the carrier additional unit, and relays L and CO are operated via the DC loop occurring at the telephone reception line to secure the calling detection. As a result, the number of relays can be decreased. At the same time, relay CO is held by the DC loop, and then the busy tone is piled on the loop to carry out the lock-out of the line. |
