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To allow the construction of hybrid systems, where the 4–20 mA is generated by the controller, but allows the use of pneumatic valves, a range of current to pressure (I to P) converters are available from manufacturers. These are usually local to the control valve and convert 4–20 mA to 3–15 psi (or 0.2–1.0 bar).
The HART Communication Protocol (Highway Addressable Remote Transducer) is a hybrid analog+digital industrial automation open protocol. Its most notable advantage is that it can communicate over legacy 4–20 mA analog instrumentation current loops, sharing the pair of wires used by the analog-only host systems.
Older teleprinters used a 60 mA current loop. Later machines, such as the Teletype Model 33, operated on a lower 20 mA current level and most early minicomputers featured a 20 mA current loop interface, with an RS-232 port generally available as a more expensive option. The original IBM PC serial port card had provisions for a 20 mA current ...
This page was last edited on 13 March 2007, at 22:35 (UTC).; Text is available under the Creative Commons Attribution-ShareAlike 4.0 License; additional terms may ...
8 mA −0.4 mA 1980 [26]: 72 Same technology as the 74AS family, but with lower power consumption at the expense of gate speed. TTL logic levels. [29]: 2–4 74AS Advanced Schottky 5 V ±10% 4.5 ns 20 mA −2 mA 1982 [26]: 72 Same technology as the 74S family, but with "miller killer" circuitry to speed up low-to-high transitions. TTL logic levels.
Wire crossover symbols for circuit diagrams. The CAD symbol for insulated crossing wires is the same as the older, non-CAD symbol for non-insulated crossing wires. To avoid confusion, the wire "jump" (semi-circle) symbol for insulated wires in non-CAD schematics is recommended (as opposed to using the CAD-style symbol for no connection), so as to avoid confusion with the original, older style ...
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A circuit diagram (or: wiring diagram, electrical diagram, elementary diagram, electronic schematic) is a graphical representation of an electrical circuit. A pictorial circuit diagram uses simple images of components, while a schematic diagram shows the components and interconnections of the circuit using standardized symbolic representations.