| 摘要 |
PURPOSE:To inform the incoming call surely, by detecting a failure produced at a part of the informing signal generating circuit and switching it to the incoming call information by the auxiliary incoming call informing section. CONSTITUTION:Assuming that the AC power supply 13, power supply 5 and wave shape section 17 are all in normal operation, and only the amplifier 12 in the informing signal generating circuit 2 is in failure. The normal incoming signal informing section 3 consisting of speakers is not alarmed. In this case, no input via the wave shape section 18 is present at the input terminal of the AND gate 16, thus the transistor 19 is off, the drive of the relay 20 is stopped, and the normally closed contact 20b is kept closed and the auxiliary incoming signal informing section 4 is alarmed in place of the normal use incoming call informing section 3. |
