December 2001 TNC Data Interfaces 8 – 13
Signal levels The signals are both transmitted and received as differential voltage.
A positive differential voltage corresponds to logic zero (OFF).
A negative differential voltage corresponds to logic one (ON).
V
dmin
= 2 V and V
dmax
= 5 V
The control unit detects the differential voltages between V
dmin
= 0.2 and
V
dmax
= 6 V as a logically defined level.
Signal designations The following signals are transmitted as differential signals:
The protective ground connects the transmitter and receiver housings.
GND is the differential voltage reference conductor.
These signals perform the same functions as those on the RS-232-C/V.24
interface.
Pin layouts The logic unit and adapter block have the same pin layout.
+ 6
+ 5
+ 2
+ 0.2
0.2
2
5
6
"0"
OFF
"0"
OFF
"1"
ON
"1"
ON
U
d
[V]
InputOutput
Signals Signal designation
Data signals TXD, TXD RXD, RXD
Control and message signals RTS, RTS CTS, CTS
DSR, DSR DTR, DTR
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