| 摘要 |
In an automatic telephone answering apparatus, an input signal sent through telephone lines is enveloped to derive pulses. The pulses are counted by a first counter. When a predetermined period of time has elapsed, a count of the first counter is compared with a reference value. When the count is larger than the reference value, the input signal is regarded as a speech signal, and the first and second counters are reset to count the pulses again. The above operation is repeated. When the count has not reached the reference value, the second counter is operated. When another predetermined period of time has elapsed, the count of the first counter is compared with the reference value, and this operation is repeated. When the count of the second counter reaches a given value, the automatic telephone answering apparatus is set in the standby mode.
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