| 摘要 |
PURPOSE:To prevent an external talking circuit from being occupied by a master set in a specific housing by providing a changeover means which measures the time of an external call for call via the external talking circuit, stops forcibly the external call when no response for the external talking exists within a prescribed time and attains internal call. CONSTITUTION:A common gate equipment M in an example is provided with a timer 37 controlled by a CPU11. This timer 37 is a timer started by the AND condition between the state of a terminal set, i.e., the master set in housing and an external call signal and transmits a timeup signal to the CPU11 when a prescribed time, e.g., 1min is elapsed. The CPU11 interrupts forcibly an external talking line during calling based on the said timeup signal and switches the master set in housing into the state possible for internal call. |
