Furuno FELCOM 70 Operator's Manual page 159

Signal descriptions
102 Signal Ground
Digital ground, return line.
103 Send Data
Data transmitted from DTE (PC) to DCE (FELCOM 70).
104 Receive data
Data Received from DCE (FELCOM 70) to DTE (PC).
105 Request To Send
OFF requests DCE (FELCOM 70) to suspend transmission to DTE
(PC).
ON requests DCE (FELCOM 70) to resume transmission to DTE (PC).
106 Clear to send
OFF indicates that DCE (FELCOM 70) cannot accept data from DTE
(PC).
ON indicates that DCE (FELCOM 70) is prepared to accept data from
DTE (PC).
107 Data Set Ready
Signal from FELCOM 70 that when ON indicates that a data call setup
is in progress.
108 Data Terminal Ready
Signal from PC. This signal is used in the Hotline mode and indicate
when going from OFF to ON that the PC wants to make a data call.
The PC clears the call by setting the signal from ON to OFF.
109 Receive Signal Indicator
Signal from FELCOM 70 that when ON indicates that connection is
established and received data will be delivered on circuit 104,
Received Data.
125 Ring Indicator
Signal from FELCOM 70. This signal is used in the Auto answer OFF
mode and when ON indicates that an incoming call is in progress. The
signal will go OFF when the call is answered by the PC by turning
circuit 108 Data Terminal Ready ON.
6. DATA COMMUNICATION
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