| 摘要 |
PURPOSE:To attain the data transmission/reception among>3 sets of data terminal equipments by using a call control signal transmission channel so as to communicate a signal transmitting/receiving the transmission right of data among terminal equipments and permitting the data transmission only to a terminal equipment obtaining the transmission right. CONSTITUTION:A subscriber line Li consists of an information transfer channel Bi and a call control signal transfer channel Di. When a transmission request I1 from a data terminal equipment Ti is received in the transmission request standby state S1, a transmission key is locked by a transmission key lock T1, a transmission right request 01 is sent to a processing unit CP as a call control signal and the mode is transferred to the transmission permission wait state S2. In informing the transmission permission 12 from the processing unit CP as a reply to the request 01, an information transfer channel is used in the step of transmission T2 to send a data, the release of the transmission right is informed to the processing unit CP by a transmission right release 02. Further, the said transmission key lock is released by the transmission key lock T3. The transmission uo permission is sent in the state S2, the terminal equipment cannot make sending operation.
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