The Models 704-OP Modular Matrix Mixers are designed to provide low cost, incremental matrix mixing of audio signals in professional, fixed installations. Outputs can be added, in increments of 6, up to a maximum of 36 (Model 704-OP). The design of the Model 704 is elegantly simple. Input circuits buffer the incoming signal, and pass the signal thru to a series of summing amplifiers. Each input may be assigned, via on-board DIP switches, to any or all summing amplifiers. Each summing amplifier will accept up to 24 separate, line level signals. Matrixes, from as small as 6 x 6, all the way up to 24 x 36, may be created. Other switching cards in the INTEGRA III SYSTEM, for example the Model 703-4 Remote Push-Button Program Selector and Volume Control, may be used to remotely select between custom matrix outputs.