PURPOSE: To enable to switch the operation mode of modulation and demodulation device to modulation side with the detected output of specific code, by connecting the output terminal of a demodulator to a terminal device through an OR circuit and adding its output to the rear end of the reception data obtained through an OR circuit to detect the specific code.
CONSTITUTION: When an FSK wave is input to a demodulator 21 via a line 14 from a central device 11, it is demodulated and becomes a reception data at a demodulator 21. The output terminal of a demodulator 21 and the input terminal of a demodulator 22 is connected to a terminal device 12 via a wired-OR circuit 25. Further, the start code added with the first reception data is detected at a start code decoder 26 and the detected output is applied to an N-bit space decoder 27. The N-bit space decoder 27 detects the specific code added to the rear end of the transmission and reception data input via the OR circuit 25, for example, detecting the space code consecutive N-bit or more, switch from demodulator to modulator with the detected output.
TAKAHASHI JIYUNICHI
NAKAZAWA MASANORI
NAKAKAWARA KIYOUICHI
KATOU HIROYUKI
TOKYO SHIBAURA ELECTRIC CO