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APPENDIX B: Electrical Interfaces
Appendix B. Electrical Interfaces
RS-530
RS-530 (EIA-530) compatibility means that RS-422 signal
levels are met, and the pinout for the DB25 connector is
specified. The EIA (Electronic Industry Association)
created the RS-530 specification to detail the pinout,
and define a full set of modem control signals that can
be used for regulating flow control and line status. The
RS-530 specification defines two types of interface
circuits. Data Terminal Equipment (DTE) and Data
Circuit-Terminating Equipment (DCE). The USB
Single-Port Hub (RS-422/485) is a DTE interface.
RS-422
The RS-422 specification defines the electrical
characteristics of balanced voltage digital interface
circuits. RS-422 is a differential interface that defines
voltage levels and driver/receiver electrical
specifications. On a differential interface, logic levels are
defined by the difference in voltage between a pair of
outputs or inputs. In contrast, a single-ended interface,
for example, RS-232, defines the logic levels as the
difference in voltage between a single signal and a
