Specifications

Appendix C - Glossary of Terms RS-422 And RS-485 Applications Ebook
Page 117 of 137 Manual Documentation Number: <DocNumber>
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Port Powered Converters
A serial/fiber optic/parallel converter which obtains it's operating power from
the input signals and handshaking lines. In Serial Converters, TD, DTR, RTS or
the DTR/DSR and RTS/CTS/CD pairs. The necessary lines must be present and
connected, they must provide enough voltage (6-7 volts) when loaded, some
models require positive voltages on RTS and DTR, others use either positive or
negative voltages.
Propagation velocity (% of c)
The speed at which an electrical signal travels in the cable. The value given
typically must be multiplied by the speed of light (c) to obtain units of meters
per second. For example, a cable that lists a propagation velocity of 78% gives
a velocity of 0.78 x 300 x 10
6
= 234 x 10
6
meters per second.
Protocol
The rules used in communicating between nodes on a network. Includes the
sequence of data requests, return data values, command set and other
standardized aspects of sending messages.
R
RD
Receive Data line in an RS-232 interface.
RDA(-)
Receive Data line A. One of two differential receive lines in RS-422 or Four-
wire RS-485 connections. The (-) line which is low compared to the (+) B line
during the Mark/Inactive state.