| 摘要 |
PROBLEM TO BE SOLVED: To obtain an information telephone terminal capable of accurately detect CPT without malfunction even in speaking by automatically adjusting a sidetone volume to be zero at the time of detecting a CPT signal. SOLUTION: At the time of detecting an incoming call from a line (S1), the line is connected by off-hooking (S2). A sidetone volume at the time of this is set to be a sidetone volume optimal at the time of a normal speech (S3). At the time of detecting (S5) a detecting signal from a CPT detecting circuit during speaking, the sidetone volume is set to be zero(S6) and the detecting signal from the CPT detecting circuit is detected again (S7). At the time, when CPT is detected again, it is judged that the CPT signal has actually come (S8). Next, processing according to a received signal is executed (S9). Then, the sidetone volume is returned to the normal one (S10) to continue speaking (S11) and speaking is finished (S12). Consequently, CTP detection is executed almost without deteriorating the quality of speaking.
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