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© Sealevel Systems, Inc. 5103 Manual | SL9075 7/2021
Appendix C
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Electrical Interface
RS-232 or EIA/TIA-232
Quite possibly the most widely used communication standard is RS-232. This implementation has been
defined and revised several times and is often referred to as RS-232 or EIA/TIA-232. It is defined by the EIA
as the
Interface between Data Terminal Equipment and Data Circuit- Terminating Equipment Employing Serial
Binary Data Interchange
. The mechanical implementation of RS-232 is on a 25-pin D sub connector. RS-232
is capable of operating at data rates up to 20 Kbps at distances less than 50 ft. The absolute maximum
data rate may vary due to line conditions and cable lengths. RS-232 often operates at 38.4 Kbps over very
short distances. The voltage levels defined by RS-232 range from -12 to +12 volts. RS-232 is a single ended
or unbalanced interface, meaning that a single electrical signal is compared to a common signal (ground)
to determine binary logic states. A voltage of +12 volts (u3 to +10 volts) represents a binary 0 (space)
and -12 volts (-3 to -10 volts) denotes a binary 1 (mark). The RS-232 and the EIA/TIA-574 specification
defines two type of interface circuits, Data Terminal Equipment (DTE) and Data Circuit-Terminating
Equipment (DCE). The Sealevel Systems adapter is a DTE interface.
