| 摘要 |
PURPOSE:To set a reference level signal appropriately, by preventing a prescribed period while a reception signal is extracted in order to set a reference level from being superposed on the timing of a ringing operation. CONSTITUTION:Immediately after applying a power source, that is, when a switch 23 is set at a closed state by an operator, a power is supplied to a control circuit 21 by a power source 22. The control circuit 21, first of all, makes a setting means 20 extract the reception signal in order to set the reference level. After completing the extraction of the reception signal to set the reference level, the control circuit 21, secondly, supplies a bell signal to a ringing means 25 after confirming the fact that the remaining power of the power source 22 exceeds a prescribed quantity. Then, the control circuit 21 makes the ringing means 25 ring for a prescribed time. Thus, by setting the prescribed period and the timing of the ringing operation of the ringing means at the front and rear by preventing them from being superposed after extracting the reception signal in order to set the reference level, the setting of the reference level can be performed appropriately simultaneously with the application of the power source, thereby, an operation can enter a reception state instantly. |
