The encoder has an enable function for use in multiplexer applications. Encoder and Decoder forced idle facilities are provided forcing a 10101010..... pattern in encode and a VDD/2 bias in decode. The companding circuits may be operated with a 3 or 4-bit algorithm which is externally selected. The device may be put in the standby mode by selection of the powersave facility. A reference 1.024MHz oscillator uses an external clock or Xtal. The FX619 is a low-power, 5 volt CMOS device and is available in 22-pin cerdip DIL, 24-lead/pin plastic and 28-lead ceramic leadless SMT packages.