| 摘要 |
PROBLEM TO BE SOLVED: To speed up data transmission by responding to connection to a digital modem or the like which is operable by an encoding system different from a ruleμor a rule (a), and converting a PCM code into an analog signal by a codec using its encoding. SOLUTION: When a 2100 Hz tone generator 320 is connected, an insertion circuit 330 uses a bit exploitation system and allocates a bit position of a 8 bit PCM code which generates 2100 Hz tone, and inserts a pattern 'P1' in the bit position. A pattern P1 detection circuit 205 of a codec 202 responds to the appearance of the 'pattern P1', activates a lead 206, a pattern P2 insertion circuit 207 transmits a P2 pattern which confirmation responds to reception of the P1 pattern to a digital modem 310, and notifies the modem 310 that there is a linear PCM code codec. Thus, in response to the connection to the digital modem or the like that operates by an encoding system different from a ruleμor a rule (a), the codec 202 converts the PCM signal into an analog signal by the encoding system.
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