User's Manual

Model CH45
EIA 422 or 485
1-6
1.2.4 Data Coupling Jumper
The Data Coupling jumper selects the electrical input conditioning; the AC position selects
capacitively coupled, the DC position is directly coupled.
AC: AC coupling has a minimum incoming data requirement of 1200 baud due to the
capacitive coupling. This option blocks DC electrical levels should the device connected
fail and ‘stick in a high level’.
DC: DC coupling allows DC logic levels to be transmitted over the fiber network, care must
be taken to guarantee that when any device stops transmitting packets that the input
level returns to a state that allows the T receptacle (emitter) to turn off. If it does not and
the IED is part of a loop, bussed or star network, the first device to transmit blocks all
other devices on the network from transmitting.
1.2.5 Biasing Resistor Jumpers
The Biasing resistor jumpers select the electrical input biasing. Biasing on RS422/485 inputs
provides the ability for the inputs to a device (the Link/Repeater) to be in a known electrical state
if the outputs that are connected to it go into a Tri-State (non driving) condition. Pins marked B
or - are pulled to +5 volts and pins marked A or + are pulled to Signal Ground. The default for
the biasing resistors is 330 Ohms, optionally 10K Ohms can be selected.
Normal:330 Ohm Biasing resistors. This is equivalent to 9 loads when configuring a bus
network configuration.
10K Ohms: 10K Ohm biasing resistors. This is the equivalent to 1 load when configuring a bus
network. This setting should be used on at least one Link/Repeater if there are 2 or
more electrically connected.
1.2.6 Logic Inversion Jumper
The Logic Inversion Jumper is located on the Link/Repeater. Use of this feature is required
when optically interconnecting IEDs using RS-232 to IEDs using EIA 422 or 485 or IEDs that
have biasing that pulls the “A” (+) line high and the “B” (-) line low during the quiescent state.
(Refer to Section 3.5)
Repeat Jumper
J3
OFF
ON
Data Coupling
Jumpers
J2J1
AC
DC
HD/FD Jumpers
J19J17J16 J18
HALF
FULL
Biasing Resistor
Jumpers
NORMAL
10K OHM
J15J13J12 J14
Logic Invert
Jumper
NORMAL
INVERTED
J10
FIGURE 4. Jumpers Settings (Factory Default Settings)