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APPENDIX I: RS232C Interface Specifications
Clear To Send - Pin 5, CTS (CB)
Direction: from modem
The CTS line indicates to the terminal that the Series II Modem will
transmit any data present on the Transmit Data line (pin 2).
Data Set Ready - Pin 6, DSR (CC)
Direction: from modem
DSR On indicates that the Series II Modem is in the data mode and is
connected to the communications channel. This signal will be on
during analog-loop-test mode.
Signal Ground - Pin 7, SG (AB)
The SG lead is connected to signal ground of the modem. It establishes
the common ground reference for all other interface signals.
Data Carrier Detect - Pin 8, CD (CF)
Direction: from modem
DCD On (positive voltage) indicates that data carrier has been received
from the other modem. This circuit will not normally turn on in the
presence of message circuit noise or out-of-band signals. There is a one
second delay between when the carrier tone has been detected and
when the CD circuit is turned on.
This signal goes off if received data carrier falls below the receiver
threshold for more than 37 mSec. When CD is off, the Received Data
circuit (pin 3) is held to the marking state.
Test Voltage - Pin 9, XV
Direction: from modem
The XV lead has 330 ohms of resistance to +12 volts DC. This lead may
be used to strap other signals high. For example, if the terminal does
not supply a DTR (Data Terminal Ready) signal, Pin 9 may be jumpered
to Pin 20 (DTR) on the RS232 connector or in the cable to force DTR
on.