Data collection apparatus of multi-drop connection type.

摘要

A master station (1) and a plurality of slave stations (2-1, 2-2,... 2-N) are connected in multi-drop connection. A carrier wave on an upstream transmission line (9) between the master station (1) and the slave stations (2-1, 2-2,... 2-N) is demodulated and remodulated in each slave station and always maintained to be on-state. Both the modulating and demodulating devices are MODEM following CCITT V.28, respectively. Each MODEM is connected to the respective slave station by a signal line following EIAR3 232C.