PSB 4860
Functional Description
Figure15 shows the signal flow graph of the echo suppression unit in more detail.
microphone
SDX
AGCX
GHX
LGAX
line out
SCAS
Attenuation
Control
SCLS
loudspeaker
LGAR
GHR
SDR
AGCR
line in
Figure 15 Echo Suppression Unit - Signal Flow Graph
State switching is controlled by the speech comparators (SCAS, SCLS) and the speech
detectors (SDX, SDR). The amplifiers (AGCX, AGCR, LGAX, LGAR) are used to
achieve proper signal levels for each state. All blocks are programmable. Thus the
telephone set can be optimized and adjusted to the particular geometrical and acoustical
environment. The following sections discuss each block of the echo suppression unit in
detail.
Semiconductor Group
31
10.97