U4082B Datasheet, PDF (8/30 Pages) ATMEL Corporation – Low-voltage Voice-switched IC for Hands-free Operation

3.8 Attenuator Control Block
The attenuator control block has seven inputs:
• The output of the comparator operated by RLO2 and TLO2 (microphone/speaker side) –
designated C1
• The output of the comparator operated by RLO1 and TLO1 (Tip/Ring side) – designated C2
• The output of the transmit background noise monitor – designated C3
• The output of the receive background noise monitor – designated C4
• The volume control
• The dial tone detector
• The AGC circuit
The single output of the control block controls the two attenuators. The effect of C1 to C4 is as
follows:
Table 3-1. Mode Selection Table
Inputs
C1
C2
C3
C4
T
T
1
X
T
R
Y
Y
R
T
Y
Y
R
R
X
1
T
T
0
X
T
R
0
0
R
T
0
0
R
R
X
0
Note: X = Do not care; Y = C3 and C4 are not both 0.
Output Mode
Transmit
Fast Idle
Fast Idle
Receive
Slow Idle
Slow Idle
Slow Idle
Slow Idle
3.9 Term Definitions
• “Transmit” means the transmit attenuator is fully on (+6.0 dB), and the receive attenuator is at
maximum attenuation (–46 dB).
• “Receive” means both attenuators are controlled by the volume control. At maximum volume,
the receive attenuator is fully on (+6.0 dB), and the transmit attenuator is at maximum
attenuation (–46 dB).
• “Fast Idle” means both transmit and receive speech are present in approximately equal
levels. The attenuators are quickly switched (30 ms) to idle mode until one speech level
dominates the other.
• “Slow Idle” means speech has ceased in both transmit and receive paths. The attenuators
are then slowly switched (1s) to idle mode.
• Switching to full transmit or receive mode from any other mode is at the fast rate (≈ 30 ms).
8 U4082B
4743D–CORD–03/06