| 摘要 |
PURPOSE:To obtain a copy in an assured way and with no hang-up although retransmission requests more than a certain number are given, by adding a command including a flag and a block number and a CRC bit to the picture information and transmitting the picture information at each block. CONSTITUTION:A shift-down condition circuit 7 is provided to a device A at the transmitter side. A transmission controlling circuit 5 receives a shift-down command from a control circuit 1 and stops the input of picture information (a) when the picture information equivalent to a frame is supplied. The circuit 1 switches an MODEM to a low-speed MODEM3 and feeds a command for request of shift- down to a device B of the receiver side via a transmitting circuit 8. The transmitter side receives the setting end signal from the receiver side and switches the MODEM to a high-speed one to command the restart of transmission to the circuit 5. As a result, the shift-down is possible under transmission of the picture information (a). This can reduce the hang-up. |
