| 摘要 |
PROBLEM TO BE SOLVED: To automatically control a received sound volume to that fitted to the call environment of a portable telephone set by always monitoring transmission frame energy transferred from a base station. SOLUTION: When an outgoing format stored in a transmission circuit 3 in the state of an automatic sound control mode, for example, is transmitted, the encoding/decoding device DSP 5 of an opposite terminal receives the outgoing format and analyzes the format. Thus, transmission frame energy is found by calculating a TCH part for the encoding/decoding of the digital sound compression of the format by a prescribed calculation expression, and transmission frame energy is informed to CPU 4. CPU 4 calculates a present noise level from the value of transmission frame energy informed from a transmission device anti the attenuation level quantity of a noise cancellor is instructed. Thus, the noise level of a transmission side is automatically analyzed on a reception side and the attenuation level is controlled, based on the analyzed value. |
