User's Manual

Models CH45
EIA 422 or 485
3-4
% of Original Pulse Multiply Factor
80% .67
60% 1.33
50% 1.67
Table 2
3.3.3 Temperature Effect
At peak operating temperatures above 65°C, the maximum number of repeats should be de-rated
by 20%. At higher temperatures the distortion caused by each repeat increases, causing the
maximum number of possible repeaters to go down.
EXAMPLE:
Peak temperature of the system will be 70°C
Running at 9600 bps
60% of original pulse width possible
initial: 100 repeats (from Figure 11)
less: 20% de-rate for 70°C
times: 1.33 for 60% pulse width
equals: 100 x 0.8 x 1.33 = 106 repeats
3.4 POWERING THE LINK/REPEATER
The Model CH45 is powered through a blade connector when inserted in the DYMEC-DynaStar 3900 15
slot Chassis: The Model CH43 has an internal DC/DC converter that isolates system and earth grounds
from signal ground on the DB9 Connector. Care must be taken when cabling not to short these together
as the SWC capabilities will be compromised.
3.5 LOGIC INVERSION JUMPERS
The Logic Inversion Jumpers are located on the unit (See Figure 1) and are standard on all Model CH45
Link / Repeaters. The Jumpers invert the polarity and logic sense of all electrical transmit and receive
signal states going to and from the 9 pin D-connector. It is set in the normal position (factory default).
When the Jumper is set to the Invert position, the protocol logic is in the inverted state.
Every CH45 Link/Repeater in the same optical network must have the Logic Inversion Jumper set to the
same position so that the quiescent state results in no light in the fiber. This feature is required when
optically interconnecting IEDs operating RS-232 to IEDs operating EIA 422 or 485; or connecting to some
EIA 422 or 485 IEDs that employ non standard logic to signal communication; or for IEDs that employ line
biasing that can cause the light to be on in the quiescent state; and can be used in all configurations.
Model CH45 is designed to operate with no light in the fiber during the communication quiescent (quiet)
state. Normal protocol for IEDs operating EIA 422 and 485 format is implemented such that the quiescent
state is achieved with the protocol at a logic low producing a potential low output. Occasionally, EIA 422
and 485 may have their output lines biased such that the “A” (+) is pulled high and the “B” (-) line is pulled
low in the quiescent state. This situation will produce a “light on” situation in the fiber during the quiescent
period. This condition is not desirable and the Logic Jumper must be set in the INVERT position to
compensate for this operation.