| 摘要 |
PURPOSE:To ensure the same service as the rotary dial telephone for the push- button dial telephone, by putting periodically the push-button dial signal receiver into the trunk which is under use. CONSTITUTION:Central control unit CC sends the order to channel control unit STCCTL to secure the connection between central office trunk COTO and push- button dial signal receiver PBREC. Then the crosspoint is closed for channel switch SWN between COTO and PBREC. After this, unit CC transmits the order to scan control unit SCNCTL to carry out the scanning for PBREC. The detection is given to the reception of the PB signal based on the result of the scanning, and thus unit CC sends the order to signal distributor SD. Then the working of relay INTO is continued to COTO to give blanking of the lamp corresponding to COTO for some time. When the user of push-button dial telephone PBTELA identifies the above blanking, the office number of COTO connected to PBTELA can be identified. |
