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A digital current loop uses the absence of current for high (space or break), and the presence of current in the loop for low (mark). This is done to ensure that on normal conditions there is always current flowing and in the event of a line being cut the flow stops indefinitely, immediately raising
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For full-duplex communication between two devices, two pairs of wires would be used. There is no common standard for current loop interfaces, so details such as timing, connectors, wire color codes, and so on, are all application specific.
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the alarm of the event usually as the heavy noise of the teleprinter not being synchronized, something that would not have been possible if the idle state had been no current flowing.
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for a current loop is limited by the available voltage. Current loop interfaces usually use voltages much higher than those found on an
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featured a 20 mA current loop interface, with an RS-232 port generally available as a more expensive option. The original
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for signaling. Current loops can be used over moderately long distances (tens of kilometres), and can be interfaced with
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interface, and cannot be interconnected with voltage-type inputs without some form of level translator circuit.
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http://www.bb-elec.com/Learning-Center/All-White-Papers/Current-Loop/Current-Loop-Application-Note/curentlp.pdf
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There are a variety of such systems, but one based on a 20 mA current level was used by the
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This article is about
Digital serial communications. For other uses, see
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standard, current loops were used to send digital data in
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181:, Industrial Press Inc., 1998,
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30:RS-232 / Current loop converter
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16:Serial communications scheme
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179:Industrial Control Handbook
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129:Electrical characteristics
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221:Communication circuits
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226:Electronics standards
120:Signaling conventions
36:serial communications
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73:. As a result, most
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75:computer terminals
71:computer terminals
52:optically isolated
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103:Teletype Model 33
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231:Serial buses
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177:E. A. Parr,
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133:The maximum
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40:current loop
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21:Current loop
114:serial port
46:instead of
215:Categories
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187:0831130857
162:References
135:resistance
65:and early
93:form for
149:See also
81:History
54:links.
48:voltage
44:current
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139:RS-232
111:IBM PC
91:serial
87:RS-232
183:ISBN
155:MIDI
38:, a
34:For
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194:^
170:^
99:mA
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Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
