ROC364 Instruction Manual
4-11 Communications
Cards
Rev
Jun/05
4.3.2 Setting Modem Card Attenuation Levels
The output attenuation of the Leased-Line and Radio Modem Communications Cards is set by default to
0 dB (no attenuation). This level can be reduced, as necessary, to better match the modem output to the
line or radio. The adjustment is made by plugging a resistor into the card at the location labeled R2.
Refer to Figure 4-9. Table 4-3 lists resistor values and the amount of attenuation they provide.
Table 4-3. Radio and Leased-Line Modem Communications Card Attenuation Levels
Attenuation
(dB)
R2 Value
(Ohms)
Attenuation
(dB)
R2 Value
(Ohms)
–2
205 K
–12
15.8 K
–4
82.5 K
–14
11.5 K
–6
47.5 K
–16
8.66 K
–8
30.9 K
–18
6.65 K
–10 21.5
K –20 5.11
K
Notes: 1. All resistor values are nominal; 1% ¼ W resistors are acceptable.
2. Attenuation for leased or private-line operation or for a GE MCS
radio is normally in this case, no resistor is needed.
3. Attenuation for a GE TMX radio is typically –20 dB.
4. Attenuation for an MDS radio is typically –10 dB.
R2
COM PORTS
Figure 4-9. Location of Attenuation Resistor
R2 Attenuation Resistor