U4082B

The low-voltage voice-switched speakerphone circuit,U4082B, incorporates the wide range of functions listedbelow. Versatility of the U4082B is further enhanced bygiving access to internal circuit points. The block diagram(figure 1) shows amplifiers, level detectors, transmit andreceive attenuators operating in complementary func-tions, background noise monitors, chip disable, dial tonedetector and mute function. Due to low-voltage opera-tion, U4082B can be operated either by a low supply or via atelephone line requiring 5.5 mA typically. Also featuredis stand-alone operation through a coupling transformer(Tip and Ring) or in conjunction with a handset speechnetwork, as shown in figure 2