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Serial Line Interface Standards
The Following is a brief description
of the Serial Line Interface Standards supported by Connect Tech Inc.
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RS-232: RS-232 *) is the most common serial line interface. All personal
computers have at least one RS-232 serial port. RS-232 is an unbalanced or
single ended peer to peer Line Interface Standard. RS-232 is ideal for connecting short
distances less than 50ft. In general RS-232 is limited to 100kb/s, but new technologies
allow for baud rates over 1Mbp/s along short distances of cable.
RS-422: RS-422 is used in situations where long distances are
required. RS-422 can drive up to 4000FT at 100kbp/s. Or short distance's over
1 Mbp/s RS-422 allows for one driver and up to ten receivers to be on a multi-dropped
network or bus. RS-422 is a differential or balanced Line Interface Standard.
RS-485: RS-485 is used in situations similar to where RS-422 is
used. RS-485 has the added advantage of allowing up to thirty two (32)
multi-dropped receivers or transmitters on a multi-dropped network or bus. Furthermore
RS-485 also permits a wire saving (1/2) duplex mode.
RS-423: RS-423 is a single ended Line Interface standard similar
to RS-232, but it permits up to 10 receivers to be multi-dropped on the same
network or bus. It can drive up to 4000ft at 100kb/s
Current Loop: Current Loop is a reliable low baud rate, 20kp/s or
less Line Interface Standard. All devices one the bus or "in the current
loop" are wired in a series circuit. Up to 10 devices can be wired in a typical
current loop circuit. The Connect Tech Current Loop SLIM offers optical isolation when
wired in "passive mode". When wired in "Active" mode a current
source on the SLIM in wired in the circuit and therefore the optical isolation is lost.
*)Note: The RS-232 is according to international
standards often also described as CCITT V.24. This contains the logic of the
interface and their signal lines. The electrical definition is in the
CCITT V.28 and the description of the 25-pin Sub d link in the
ISO 2110.
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