B-4
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Serial Interconnections
B
Notes
1. A high EIA-232-D signal level is +3 to +15 volts. A low level is
−
3
to
−
15 volts. Connecting units in parallel may produce out-of-range
voltages and is contrary to specifications.
2. The EIA-232-D interface is intended to connect a terminal to a
modem. When computers are connected without modems, one
computer must be configured as a modem and the other as a
terminal.
22
RI
Ring Indicator. Output from modem to terminal; indicates that an incoming
call is present. The terminal causes the modem to answer the phone by
carrying DTR true while RI is active.
23
Not used.
24
TxC
Transmit Clock (DTE). Input to modem from terminal; same function as
TxC on pin 15.
25
BSY
Busy. Input to modem from terminal; a positive EIA signal applied to this pin
causes the modem to go off-hook and make the associated phone busy.
Table B-1. EIA-232-D Interconnect Signals (Continued)
Pin
Number
Signal
Mnemonic
Signal Name and Description