U4091BM-R datasheet(19/38 Pages) ATMEL

19 / 38 page

4872A–CORD–08/05

U4091BM-R

Note:

X = don’t care; Y = I3 and I4 are not both noise.

12.4

Term Definitions

Transmit means the transmit attenuator is fully on, and the receive attenuator is at max-

imum attenuation.

Receive means the receive attenuator is fully on, and the transmit attenuator is at max-

imum attenuation.

In idle mode, the transmit and receive attenuator are at half of their maximum

attenuation.

– Change mode means both the transmit and receive speech are present in

approximately equal levels. The attenuators are quickly switched (30 ms) to the

opposite mode until one speech level dominates the other.

– Idle means speech has ceased in both transmit and receive paths. The attenuators

are then slowly switched (1.5s) to idle mode.

Switching to full transmit or receive modes from the idle mode is done at a fast rate

(30 ms).

Table 12-1.

Mode Decision for Signal Sensing

Input

Output

Mode

Transmit

Change mode

Receive

Idle

RNN

Idle

LOGT > CLOGR

I1 = T

LOGT < CLOGR

I1 = R

LOGR < CLOGT

I2 = T

LOGR > CLOGT

I2 = R

BNMT detects speech

I3 = S

BNMT detects noise

I3 = N

BNMR detects speech

I4 = S

BNMR detects noise

I4 = N

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