EIA-423

communications, standard (Formerly "RS-423") An EIA

serial line standard which specifies single ended

communication. The mechanical connections for this interface

are specified by EIA-449. Although it was originally

intented as a successor of EIA-232 it is not widely used.

The EIA-232 standard has its limits at 20kbps and 1.5m.

EIA-423 can have a cable lenght of 1200m, and achieve a data

rate of 100Kbps. 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

bits. A "break" condition is a continuous logical one on the

line which is what would be observed if nothing was connected.

Comparing EIA-422, 423, 449 to RS-232-C. Detailson RS-232, 422, 423 and 485.

(2002-10-05)