| 摘要 |
PURPOSE:To add a MODEM so that an optional slave station is used as a control station of the polling system and an optional station out of other slave stations and a master station is used as a subordinate station, by providing newly a circuit which gives always the rransmission request to the MODEM and gives always the transmission permission to a data terminal equipment. CONSTITUTION:In the normal state, since the transmission request is not gen- erated from a data terminal equipment 6 in a master station, a receiving data switching circuit 13 is so operated that receiving data from a MODEM 1 is folded as transmission data to the MODEM 1. Under this state, if a data terminal equipment 8 of a slave station transmits a polling sequence as a control station of the polling system, this sequence is transmitted to an up line 11 through a MODEM 3 and is received by the MODEM 1 and is given to the MODEM 1 again as transmission data through transmission data/receiving data switching circuit 13. Meanwhile, since the transmission request is always given to the MODEM 1 by a transmission request and transmission permission supplying circuit 14, the polling sequence transmitted from the data terminal equipment 8 is transmitted to all terminal equipments in the result. |
