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Figure-8
Wiring to Field Device
Half Duplex Wiring Configuration:
Justification for a half-duplex wiring configuration is, of course, the reduced number of
conductors necessary for interconnection. The economic factors become obvious when
considering cable runs of half a mile distance or more. With this configuration, it
becomes necessary for the controlling electronics to enable and disable the relevant
transmitters at appropriate times based upon the software system protocol. Otherwise,
there is a possibility that line contentions might occur with two or more transmitters
attempting to 'talk' at the same time.
Another possibility is to have an arrangement where one end only has a transmitter
attached, and the opposite end only has a receiver attached (not shown). Implementation
and utility of this type of unidirectional system will depend on the user application.
Figure-9
Point-to-Point Half Duplex Wiring
