Appendix D – Pin Descriptions
Multi-Tech Systems, Inc. MT5600BA-V92 User Guide 54
Appendix C - Pin Descriptions
RS-232 Pin Descriptions
CGND is tied common to GND on the modem’s PCB
Transmitted Data The DTE uses the TD line to send data to the modem
for transmission over the telephone line or to transmit commands to the
modem.
Received Data The modem uses the RD line to send data received from
the telephone line to the DTE and to send modem responses to the DTE.
Request to Send is used for hardware flow control.
Clear To Send is controlled by the modem to indicate whether or not the
modem is ready to transmit data. CTS high indicates to the DTE that
signals presented on TD will be transmitted to the telephone line. CTS
low indicates to the DTE that it should not transfer data across the
interface on TD.
Data Set Ready indicates modem status to the DTE. DSR low indicates
that the DTE is to disregard all signals appearing on the interchange
circuits except Ring Indicator (RI). It reflects the status of the local data
set, and does not indicate an actual link with any remote data
equipment.
Carrier Detect used to signal to the DTE that a carrier has been detected.
A positive voltage output from the modem used for tests or for strapping
signals high if needed.
Transmit Clock output from modem, used in synchronous mode.
Receive Clock output from modem, used in synchronous mode.
Analog Loop input to modem to enable analog loop test.
Data Terminal Ready input to modem from DTE to control answering and
disconnection of modem.
Remote Digital Loop Input to modem to enable RDL test.
Ring Indicator output high indicates the presence of a ring signal on the
telephone line.
External Clock input to modem used in special synchronous applications.
Test Mode output from modem to indicate modem is in one of the test
modes.
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