| 摘要 |
PROBLEM TO BE SOLVED: To provide a portable telephone terminal equipment capable of giving optimum echo return loss E.R.L. to an echo cancellation circuit even when a vehicle or a mount position differs. SOLUTION: In the case of attaching this terminal equipment 20 to a vehicle, the terminal equipment is initialized. An initial setting state signal is given to an initial setting signal input 24 of a microcomputer 25. Upon the receipt of the signal, the microcomputer 25 replaces an output of a speaker amplifier 26 with an output of a reference voice generating source 22. The output is picked up by a microphone 4, a microphone input is rectified by a full wave rectifier circuit 23 and the rectified signal is applied to an A/D input of the microcomputer 25. The microcomputer 25 variably controls a gain of a microphone input adjustment section 27 in response to an output level of the full wave rectifier circuit 23 to set the optimum E.R.L. value to an echo cancellation circuit 21a.
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