| 摘要 |
PURPOSE:To improve the utilizing efficiency of a line, so long as the line state permits, by setting selectively the length of preamble and completing the preamble when a code included in the preamble corresponds to the set length. CONSTITUTION:A preamble PAB 14 includes an N-bit binary code and the length is set with switches S1-S3 in response to the state of the line. For example, the S1 is closed, the S2, S3 are opened and a PAB length load signal LL is inputted, then a counter 104 is preset to 001. When a counter 102 counts a clock CLK by 8-pulse, a signal Y7 is outputted to an output of a 3-8 decoder 106 and a binary counter 104 is advanced. When the counter 104 counts a signal Y7 by 7, the counter 102 counts 54 pulses of CLK until that time, binary outputs of the counter 104 go all to high level, a decoder 108 detects it, and keeps the output 138 as high level, and 54-bit of the PAB 14 is outputted from an output 140, allowing to complete the output. |
