Abstract : This thesis investigates implementation of the main function of the subscriber interface card for the European standard E1 multiplexer using standard and compressed voice techniques. This is achieved by the design and implementation of a microcontroller based system that has the ability to control and program the codec/filter function of the card using new codec/filter integrated circuit. It also provides the user with a mean to interact with the card. The card was constructed to meet the basic requirements of ITU-T Recommendation G.703, G.711 and G.726 related to the clock interface, Pulse Code Modulation (PCM) of voice frequency and Adaptive Differential PCM (ADPCM) transcoding technique for the voice compression. Two cards are built corresponding to the transmitter and receiver sides for testing the performance. Their functions were defined in regard to the clock and the status information, which determine the encoding and decoding algorithms for the original and the reconstructed signals respectively. The card was designed, implemented and checked successfully for different compressions by observing the timing diagrams, original and reconstructed signals and communicating through telephone handset.