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MSM6889

¡ Semiconductor

Figure 3

The modulation analog signal and PB tone from the modem are not sent at a time. The signal to

be sent is determined by the operating mode specified.

This device is provided with the pins for specifying levels of these transmit signals independently.

The answer tones, which are generated from MODULATOR, are handled as modem signals.

VM : Modem signal level (voltage) at MOD (pin 9)

VP

: PB tone level (voltage) at PB (pin 10)

When the external resistors are R4, R5 and R6, the signal levels at AO (pin 5) are as shown below.

Note : R4, R5, R6

≥ 20 kW

As described in "Resistance Hybrid Condition", signal levels actually sent over a phone line will

be half the above mentioned values under the ideal condition.

Setup of Transmit Signal Levels

5

8

7

10

9

VAO

R4

R5

R6

VP

VM

AO

GAT2

GAT1

PB

MOD

PB Tone

Generator

Modulator

R4,R5,R6 ≥ 20 kW

LPF

+

_

VAO (modem) =

R4

¥ VM

R5

VAO (PB)

=

R4

¥ VP

R6