| 摘要 |
PURPOSE:To inform the cause to an error of communication by displaying the progressing stateof the control procedure so as to sweep out the care or a user. CONSTITUTION:A signal from a telephone line 1 is inputted to band pass filters BPFs 5, 6, 7, 8, their outputs are outputted from signal lines 13a, 13b, 13c, 13d via full wave rectifier circuits 9, 10, 11, 12. A signal sent from a receiver is amplified by an amplifier 3 via the line 1 and a switch 2. The output is outputted to a signal line 13 via a BPF and a rectifier circuit. The control circuit (microcomputer) 17 discriminates the frequency of the output from the signal line 13 and its arrival sequence and outputs a signal for the display to signal lines 14a-14p. Light emitting elements 15a-15p are connected respectively to the signal line 14, and they are provided respectively to display boards 16a-16p. For example, when the dislay board 16h is lighted and the display board 16p is lighted, the occurrence of an error is discriminated.
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