Furuno IB-681 - Manual (Page 25)

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3.4.4 Automatic call clear sequence
An automatic call is cleared when the DTR signal is received from the HSD terminal.
The HSD terminal turns off DTR, then the automatic call is cleared.
The HSD terminal sends clear signal to CES, then HSD modem turns off DCD and
CTS. Finally HSD modem turns off DSR.
CES NCS FELCOM
HSUB
Ch. release SU
CESI
Ch. release SU
DTR OFF
DCD CTS OFF
DSR OFF
10 times
Disconnect
Figure 8 Automatic call clear sequence
3.4.5 Call clear sequence from land
Land clears automatic call, then CES sends clear signal. The HSD modem turns off DCD
and CTS. Finally, the HSD modem turns off DSR, and the HSD terminal turns off DTR.
CES NCS FELCOM
HSUB
Ch. release SU
CESI
Ch. release SU
DTR OFF
DCD CTS OFF
DSR OFF
HSUB
Disconnect
from land
Ch. release SU
10 times
Max. 2 min
delay
Figure 9 Call clear sequence from land