SL34118

System Logic

Semiconductor

SLS

Voice Switched Speakerphone Circuit

The SL34118 Voice Switched Speakerphone Circuit incorporates

the necessary amplifiers, attenuators, level detectors, and control

algorithm to form the heart of a high quality hands-free speakerphone

system. Included are a microphone amplifier with adjustable gain and

MUTE control, Transmit and Receive attenuators which operate in a

complementary manner, level detectors at both input and output of

both attenuators, and background noise monitors for both the transmit

and receive channels. A Dial Tone Detector prevents the dial tone

from being attenuated by the Receive background noise monitor

circuit. Also included are two line driver amplifiers which can be used

to form a hybrid network in conjunction with an external coupling

transformer. A high pass filter can be used to filter out 60 Hz noise in

the reseive channel, or for other filtering functions. A Chip Disable pin

permits powering down the entire circuit to conserve power on long

loops where loop current is at a minimum.

The SL34118 may be operated from a power supply, or it can be

powered from the telephone line, requiring typically 5.0 mA. The

SL34118 can be interfaced directly to Tip and Ring (through a coupling

transformer) for stand-alone operation, or it can be used in

conjunction with a handset speech network and or other features of a

featurephone.

• Improved Attenuator Gain Range: 52 dB Between Transmit and

Receive

• Low Voltage Operation for Line-Powered Applications (3.0-6.5 V)

• 4 Point Signal Sensing for Improved Sensitivity

• Background Noise Monitors for Both Transmit and Receive Paths

• Microphone Amplifier Gain Set by External Resistors - Mute

Function Included

• Chip Disable for Active Standby Operation

• On Board Filter Pinned-Out for User Deined Function

• Dial Tone Detector to Inhibit Receive Idle Mode During Dial Tone

Presence

ORDERING INFORMATION

SL34118N Plastic

SL34118D SOIC

° to 70° C for all packages

PIN ASSIGNMENT