The present invention provides for the compression of digital and analog data for storage and transmission. Analog data in the form of an analog signal (3) is converted into a digital signal (6) by an analog-to-digital converter (5). The digital signal (6) is then converted into an analog signal having an alternating frequency (13) by a first converter processor (7) and an alternating frequency generator (11) according to a predetermined conversion table (9). To reproduce the original analog signal (3), the analog signal having an alternating frequency (13) is first converted back into a digital signal (6) by an alternating frequency measurement means (21) connected to a second converter processor (23), also in accordance with the predetermined conversion table (9). The digital signal (6) is then converted to the original analog signal (3) by a digital-to-analog converter (25).