A miniature compandor for general use in wire and radio communication systems

A miniaturized compandor has been developed for widespread application to open-wire, cable, and radio channels. Self-contained plug-in units can be inserted in telephone circuits at all commonly expected transmission levels. Two-wire operation is achieved with a plug-in resistance hybrid. Equipment simplification is achieved through use of only two miniature vacuum tubes. A conventional approach has been followed to obtain a compandor circuit with a two-to-one compression and expansion characteristic. Straightforward empirical methods are used to achieve the desired results. Reduction of noise and crosstalk, commonly stated as 22 decibels (db), actually varies considerably, depending on the type and magnitude of interference.