User's Manual
Model CH45
EIA 422 or 485
1-3
Full Duplex Communication:
Simultaneous transmit and receive communications.
T:
Transmit optical port.
TE:
Diagnostic LED that illuminates when the Link/Repeater is receiving an electrical transmit from
its IED.
TO:
Diagnostic LED that illuminates when the Link/Repeater is transmitting a signal optically.
R:
Receive optical port.
RE:
Diagnostic LED that illuminates when the Link/Repeater is delivering a received optical signal
electrically to the IED.
RO:
Diagnostic LED that illuminates when the Link/Repeater is receiving a signal optically.
Optical Budget:
The optical budget is expressed in dB and is the amount of light loss tolerated for
communication. The total distance between two devices that a signal can be transmitted is
determined by subtracting all the losses of the optical circuit from the optical budget. Various
factors in the optical circuit attenuate the light transmission and must be accounted for to assure
a reliable optical circuit. Key factors include cable attenuation (expressed as dB per unit length),
cable aging, and cable fittings (terminations, splices, splitters, etc.).
Non Return to Zero (NRZ):
This type of encoding scheme does not require the voltage potential of each data bit to return to
the zero potential. No clock or timing recovery is provided with this type of communication
except in the start and stop bits usually found on each data word.
Return to Zero (RZ):
This type of encoding scheme requires the voltage potential of each data bit to return to the zero
potential. This allows timing recovery with each bit instead of just the start and stop bits of the
data word.
Number of Repeats:
The Number of Repeats is the number of Link/Repeaters that may be connected in a network
when the Repeat function is required such as in loop configurations. The sum of Slaves in a
Master/Slave loop is the number of repeats for that type of loop. The number of Peers minus
one is the number of repeats in a Peer-to-Peer loop.
Asynchronous Communication:
This type of communication does not transmit a separate clock signal with the data signal.
Link/Repeaters support asynchronous communication only. A communication scheme where
the clock needs to be transmitted (Synchronous Communication) is not supported unless the
clock is embedded with the data.