Programmable calculator to use magnetic strips were the HP-41C and TI-59. Continuous memory does not lose its content when the calculator is switched off. With continuous memory the user can, for example, change batteries without losing the entered programs. Compact Cassettes offered a simple, inexpensive alternative to magnetic cards. Usually, an interface module, such as the Casio FA-1, was used to connect the calculator to an ordinary cassette recorder and digital data were encoded as frequency-shift keyed audio signals. Sharp and Hewlett-Packard also sold dedicated micro- or mini-cassette recorders that connected directly to the calculator. These set-ups, while being more practical and
Sumlock ANITA calculator of models of desktop calculators that followed, which gradually moved to transistor and integrated circuit technology, and from the early 1970s, the hand-held models. In 1966 the calculator manufacturing operation of the Bell Punch Company was formed into a separate company, called Sumlock-Anita Electronics, and continued to manufacture both the mechanical and electronic calculators, still marketed by its Sumlock Comptometer division. There was a major development in 1973 when the Sumlock Anita Electronics division was bought by its main supplier of integrated circuits, Rockwell International of the U.S.A. The remainder of the Bell Punch Co. continued manufacturing and selling its