TS4000 Radio Modem User’s Manual
Appendix A - Serial Ports
79
pin can be set to always be in the active high state. In this case the pin is
internally connected to +5 volts through a 1 K
Ω
resistor.
[4] For standard RS-232 ports this pin is the Ring Indicator (RI) line, which is an
output for DCEs (the TS4000). However, the TS4000 does not have an RI
line internally. Instead, this pin can be connected to the serial port Data Set
Ready (DSR) line which is an output for DCEs (output of the TS4000), or this
pin can be setup to provide DC power into the TS4000.
The use of this pin as a power pin is non-standard and therefore care should
be taken when connecting the TS4000 to standard serial devices. For most
serial ports this is not a problem because RI is a modem (DCE) output and
the TS4000 power supply mostly falls within the allowed voltage range for
RS-232 signals. Therefore the power voltage on this pin is interpreted as an
active RI signal. For systems that use the RI signal differently, or that cannot
operate with power on this pin, this pin should be disconnected between the
TS4000 and the host equipment.
[5] For the watertight version of the TS4000, the alternate jumper block option to
supply power to the modem via this pin should not be used due to the
amperage limitation of the flex circuit connecting the LEMO connector to the
modem board.
Signal
Connector
Pinout
Direction
Signal Name
Mnemonic
9 Pin
25 Pin
DCE
DTE
Signal Ground
SG
5
1, 7
--
--
Transmit Data
TD
3
2
Input
Output
Receive Data
RD
2
3
Output
Input
Request to Send
RTS
7
4
Input
Output
Clear to Send
CTS
8
5
Output
Input
Data Carrier Detect
DCD
1
8
Output
Input
Ring Indicator
RI
9
22
Output
Input
Data Set Ready
DSR
6
6
Output
Input
Data Terminal Ready
DTR
4
20
Input
Output
Standard RS-232
Serial Port Pinout
Signal Description
Request to Send (RTS)
Request for transmission from the DTE.
Clear to Send (CTS)
Response (to the Request to Send) from the DCE
indicating a readiness to transmit data.
Data Carrier Detect (DCD)
Status from the DCE indicating that it is receiving.
Ring Indicator (RI)
Status from the DCE indicating that it has
detected the ring state.
Data Set Ready (DSR)
Status from the DCE indicating that it is
operational.
Data Terminal Ready (DTR) Status from the DTE indicating that it is
operational.
Standard Usage of
the RS-232 Control
Signals
