Bogen Models C10 and C20 public address amplifiers are rated at 10 and 20 watts, respectively, and are UL and C-UL listed. The amplifiers accommodate low-impedance microphones and high-impedance auxiliary sources. A front panel selector switch offers a choice of either two low-impedance balanced microphones (MIC1, MIC2), or one microphone and one auxiliary input (MIC1, AUX). The AUX input can be muted when a customer-supplied SPST normally open switch is used for microphone precedence. Independent volume controls and a treble control, for tonal balance, are provided. Balanced and unbalanced outputs are provided for 4-, 8-, and 16-ohm speakers and for 25- and 70-volt constant voltage systems. An accessory transformer, Bogen Model WMT1A, can be installed to provide input and output matching to a telephone line.