MC34018

LINEAR INTEGRATED CIRCUIT

UNISONICTECHNOLOGIESCO.,LTD

4 of 8

www.unisonic.com.tw

QW-R108-006.E

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PIN DESCRIPTION(Cont.)

PIN NO.

PIN NAME

DESCRIPTION

23

XDC

Transmit detector output. A resistor and capacitor at his pin hold the system in the transmit

mode during pauses between words or phrases. When the XDC pin voltage decays to

ground, the attenuators switch from the transmit mode to idle mode. The internal resistor at

XDC is nominally 2.6k ohms(see Fig.1).

24

VLC

Volume control input>connecting this pin to the slider of a variable resistor provides receive

mode volume control. The VLC pin voltage should be less than or equal to VB.

25

ACF

Attenuator control filter. A capacitor connected to this pin reduces noise transient as the

attenuator control switches level of attenuation.

26

RXO

Receive attenuator Output. Normally this pin is ac coupled to the input of the speaker

amplifier.

27

RXI

Receive attenuator Input. Input impedance is nominally is 5.0kΩ.

28

RRX

A resistor to ground determines the nominal gain of the receive attenuator. The receive

channel gain is directly proportional to the RRX resistance.

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BLOCK DIAGRAM