10
3.
Rotate the GAIN/EDIT knob to select the serial mode then push the GAIN/EDIT knob to save the set-
ting.
Note that the RS-485, RS-422, and I2C ports on the preamplifier use different pin configurations than the RCU. Please be careful to
use the correct wiring for your m802 system. Refer to the connector pin diagrams in the cable diagrams section p22 .
reMote control Unit
m802RCU remote controls with serial number R802171 and above are equipped with RS-485 / RS-422 serial
ports. These units also contain the original
I
2
C
serial ports and are backwards compatible with previous m802
systems.
The m802RCU comes from the factory in RS-485/RS-422 communication mode. If
I
2
C
operation is desired for
controlling older m802 preamplifiers then the software must be set for
I
2
C
mode. To change the communica-
tions mode do the following:
4.
With the RCU’s power supply unplugged from the barell jack, push and hold the first three leftmost
top row buttons ( + ch1 + ch2).
5.
While holding, insert the power supply plug. The RCU screen will display the current function of the
serial port.
6.
Release the three buttons, rotate the GAIN/EDIT knob to select the serial mode, then push the GAIN/
EDIT knob to save the setting.
tHe aDvantaGeS of USinG tHe m802 in rS-485 / rS-422 MoDe
1.
Ground isolation - The RS-485/RS-422 ports on the m802 preamplifiers are ground isolated. This en-
sures that there are not ground loops created in the control wiring of the m802 system. This is espe-
cially helpful in situations where there are multiple m802 preamplifiers in distributed locations.
2.
Differential signaling - Since RS-485/RS-422 is based on a balanced differential signal it radiates far
less noise than the older
I
2
C
connection. This means that control signals will be less likely to pollute
audio signals in adjacent wiring.
3.
Longer distance - The RS-485/RS-422 signals can run over very long lines. Control signals can be eas-
ily sent over 1000 meters (3937’)
4.
Compatibility - With RS-422 the m802 control signals can be transported over various standard data
links. This includes optical fiber media combiners.
m802 Preamplifier
m802 RCU
m802 Preamplifier
m802 Preamplifier
m802 to preamplifier control data connections
