The SA2531 is a CMOS integrated circuit that contains all the functions needed to form a high performance electronic telephone. The device incorporates LD/MF repertory dialling, melody generation, ring frequency discrimination and a high quality speech circuit. A RAM is on chip for a 31 digit last number redial and 14 memories each containing up to 21 digits. The sliding cursor procedure makes Last Number Redial easy behind a PABX. The SA2531 (exept the SA2531D) incorporates a volume control for the earpiece. The receive volume can be controlled by the VOL key (+4dB) or by the +/- keys (+6dB/-4dB in 5 steps). The versatility of the circuit is provided by on chip programmability and a few external components. This allows easy adaption to different PTT requirements without changing the PCB of the telephone.