Furuno DP-6 manual Termination of Communication, ARQ mode traffic exchange timing

not sending. This time is taken up by propagation time from the ISS to the IRS, 70 ms for the IRS to send its service information signal, and the return trip back to the ISS.

The IRS listens between blocks and sends a control signal (CS1 or CS2) to request either the next block, or retransmission of the last block in the case of error. Request for retransmission may be re- peated up to 32 times, until the completed block has been received error-free. After 32 times, the ISS automatically initiates a new call.

INFORMATION

3 Characters

70 ms

210 ms

CONTROL SIGNAL

1 Character

70 ms

450 ms

Figure 1-2 ARQ mode traffic exchange timing

Once an entire message is received (error-free), a station may switch its function from the IRS to the ISS by means of a control signal (CS3). This change is done by either the ISS by the sequence of " Figure shift + ? ", or by the IRS operator by activating the "OVER"

control. Upon receipt of CS3, ISS answers with a block. This switches the ISS into IRS. However, the original Master and Slave stations' status remains unchanged, since the Master Station al- ways controls the radio circuit.

Termination of Communication

Only the ISS may terminate the established circuit. It does this by sending three "idle signals ." The IRS and ISS exchange control signals, each reverting to standby after acknowledging each other’ s control signals. Then, the connection is cleared.

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