| 摘要 |
PURPOSE:To attain the external setting of a threshold level by constituting the frequency discrimination circuit by a hardware. CONSTITUTION:A shift register 15 applies serial/parallel conversion to a PCM code. A comparator 42 compares a threshold level specified by a signal in total 4-bit fed to input terminals 43-46 with a negative mu-1aw signal as an output signal of an exclusive NOR gate 41, and the count of a frequency recognition counter composed of the low-order 3-bit of the 8-bit D-FF 17 and an adder 51 is stopped. A large capacity ROM is excluded by constituting the circuit equivalent to the content of a ROM to attain the circuit integration.
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