| 摘要 |
<p>PURPOSE: To accurately extract a caller ID from a transmission signal without the use of a special hardware by storing sequentially bits discriminated other bits than a start bit and a stop bit to a memory and outputting the stored bits as code data. CONSTITUTION: When an NCU 2 detects a first CI signal in the caller ID extract processing, an interruption is started by a CPU 3. At first the content of a buffer 6 is cleared in the initializing processing. Then a timer for checking reception time expiration is started and a tone detector is set. Then whether or not the reception time is expired is discriminated. Before that, whether or not a sampling time is expired is discriminated in a short period. In the case of YES, the sampling time is set again. Then an output port of a MODEM 5 is checked to discriminate a tone. When the tone corresponds to '1', a level 1 is outputted to an A register. When the tone corresponding to '0' is discriminated, a level 0 is outputted to a 1st shift register and whether or not 8-bit data are made complete is discriminated, and in the case of YES, data reception processing is executed and then the reception is finished.</p> |
