4RF Aprisa XE User Manual page 107

3. Set the Q4EM Output level and the Input level required.
Signal Direction
Input level (L )
i
Output level (L )
o
It is important that analogue signals presented from the Q4EM interface be normalized to fit within the ±
127 quantizing steps of the encoder. This is done by adjusting the circuit levels relative to the 0 dBm
(± 118 peak code) for example:
If a nominal input level of -6.0 dBm is applied to the Q4EM interface input port, the Q4EM Input
Level must be set to -6.0 dBr. This will effectively amplify the sent signal by 6.0 dB to produce a
digital signal with a ± 118 peak code (0 dBm).
If a nominal output level of -6.0 dBm is required from the Q4EM interface output port, the Q4EM
Output Level must be set to -6.0 dBr. This will effectively attenuate the received decoded signal
by 6 dB.
4. Set the Q4EM E wire interface to either Normal or Inverted.
This determines the state of the CAS bit relative to the state of the E wire:
E wire output
Output Active
Output Inactive
5. Set the Q4EM M wire interface to either Normal or Inverted.
This determines the state of the CAS bit relative to the state of the M wire:
M wire input
Input Active
Input Inactive
6. Click Apply to apply changes or Reset to restore the previous configuration.
7. Select Q4EM PCM Law Control from the Quick Links box.
This option sets the companding law used by the four ports on the Q4EM card.
A-Law is used internationally (default).
µ-Law is used in North America and Japan.
Note: The PCM Law Control controls all four ports on the Q4EM card. To run a mixture of µ-Law and A-
Law interfaces, multiple Q4EM cards are necessary.
Level adjustment range
-14.0 dBr to +4.0 dBr in 0.5 dB steps
-14.0 dBr to +4.0 dBr in 0.5 dB steps
CAS bit Normal
(default)
0
1
CAS bit Normal
(default)
0
1
Aprisa XE User Manual
Configuring the Traffic Interfaces | 105
Default setting
+0.0 dBr
+0.0 dBr
CAS bit Inverted
1
0
CAS bit Inverted
1
0