The TOA W-906A and W-912A Mixer Power Amplifiers control and mix up to six independent input signals plus two inputs with use of expanding kit. The W-906A delivers up to 60 W of output power and the W-912A 120 W. Optional accessory modules are available for use with the W-906A and W-912A to provide versatility for a wide range of operating applications. Edge connectors at the bottom of the front panel permit the selection of the TOA plug-in modules. (Please contact your local TOA dealer for details on TOA plug-in modules.) The W-906A and W-912A have a built-in one-octave graphic equalizer with 9 bands to tailor sound system frequency response to room acoustics, reducing feed-back tendencies and improving intelligibility. A built-in compressor circuit is provided to protect the output level from distortion as a result of excessive input and keeps it constant. Compressor's threshold level can be adjusted. The W-906A and W-912A Mixer Power Amplifiers have output terminals to match 4 or 8 speaker systems, or speaker distribution system may be connected to the 25 or 70 V terminals. User's (blank) space is provided for additional functions to be made by the customers. The expanding kit (optional) may be loaded in this space when the number of input is increased. Protection against tampering is assured by means of a key-locked hinged door.