| 摘要 |
1,232,441. Digital transmission systems. WESTERN ELECTRIC CO. Inc. 8 July, 1968 [7 July, 1967], No. 32419/68. Heading H4P. [Also in Division G4] In a digital transmission system comprising a control station and a number of way-stations connected to a common line, the control station sends a message to selected way-stations and subsequently polls these way-stations to determine whether or not they have received the message correctly. When the control station has a message to transmit it sends a " start of heading " signal which alerts all the way-stations. It then sends the heading, consisting of the addresses of the way-stations to receive the message. These addresses are stored in an address store at the control station, and cause the addressed waystations to select their printers. The control station now sends a " start of message " signal, which enables the selected printers, followed by the message, which is recorded by the printers, and an " end of message " signal which inhibits the printers. The control station now polls in turn the way-stations whose addresses are in the store. When polled a way-station returns a signal indicating whether or not the message was received correctly-this is determined by checking that a universal contact operated whenever a message character was received. If reception was correct the polled address is removed from the store but if it was not correct the address is retained. The next stored address is now polled, and the cycle repeated until all stored addresses have been polled. The addresses remaining in the store at the end of polling are those of way-stations which did not receive the message correctly. An " end of transmission " signal from the central stations places all the way-stations in the rest state and clears the address store. |
