User Guide

After Sales
Technical Documentation
System Module
THX–4
Amendment 10/97Page 4–14
Name Description
MICAMP Signal from the microphone is fed to this stage and
amplified
MUX TX source selection (EXMIC/MIC/DTMF/MUTED)
TXAAFIL Anti alias filter (see NANTIC specification)
BANDPASS (see NANTIC specification)
TXATT For handsfree mode of operation
COMPRESSOR 2:1 syllabic compressor
PREEMP Pre–emphasis filter
AGC Soft Limiter
LIMU Hard limiter
LOWPASS Low pass notch filter
POSTFIL Second order Sallen–Key filter
SUMSTAGE Data from modem is summed in here
TRCOMP Modulation sensitivity compensation
Receiver (RX) Signal Path
The demodulated audio signal (DAF) from the receiver is fed to the
NANTIC circuit which contains a software controlled receiver and
compensation amplifier. The output of this stage drives the modem IC
and the remaining NANTIC RX signal processing stages.
Name Description
MUX RX source selection (DTMF/DAF1/DAF2)
RXAAFIL Anti alias filter
RXFIL Second order Sallen–Key filter
EXP 2:1 Syllabic Expander
VOLUME Volume Control Amplifier
RXATT For Handsfree mode
EARPAMP The earphone amplifier is a single input, differential
output amplifier for a ceramic earpiece
ACCAMP Accessory amplifier – buffer for XEAR output