RS-423

A common electrical specification for the signals on a {serial

line}. When no data is being transmitted, the serial line is

at a logical zero (:3 to :15 Volts). A logical one is

represented as a signal level of -15 to -3 Volts. In

practise, one often finds signals which switch between

nominally :4.5 and :0.5 Volts. Such signals are large by

modern standards, and because the impedance of the circuits is

relatively high, the allowable {bit rate} is modest.

The data is preceded by a {start bit} which is always a

logical one. There may be seven or eight bits of data,

possibly followed by an even or odd {parity} bit and one or

two {stop bit}s.

A "break" condition is a continuous logical one on the line

which is what would be observed if nothing was connected.

{EIA-232} specifies the physical connector normally used for

RS-423 lines.

(1995-02-02)