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Modem 3600 2-5
7 AB 102 Signal
Ground
Signal or common signal and dc
power ground. **
8 CF 109 Receive
d Line
Signal
Detector
A positive level from the modem
indicating the presence of a
received signal (carrier detect). *
9-- +12
Vol t s
+12 voltage reference
10 -- -12 Volts -12 voltage reference
11 -- Signal
Quality
Indicator
This circuit indicates probability
of errors in the received data: a
positive level indicates poor signal
quality while a negative level
indicates good signal quality. †
15 DB 114 Trans-
mit
Clock
(DCE)
A transmit data rate clock output
for use by an external data source:
Positive clock transitions
correspond to data transitions.
17 DD 115 Receive
Clock
A receive data rate clock output
for use by an external data sink:
Positive clock transitions
correspond to data transitions.
18 -- 141 Local
Loop-
back
A positive level causes the modem
to enter the local analog loopback
test mode.*
Table 2-1. Pin Signal Descriptions (Continued)
Pin
EIA-
232D
CCITT
V.24 Signal Description
*
* Modem options may force these signals on or cause them to be ignored.
*
** Refer to Appendix C, Hardware Options.
*
† This function can be disabled or its logic sense reversed by hardware straps.