Abstract: An electrical to acoustic transducer utilizing the piezoelectric qualities of a polymer lamina and an arrangement including an amplifier and network to compensate for the polymer variability. This is accomplished by first providing two sets of electrodes on the surfaces of the polymer, a first set for driving the polymer and a second set for sensing the polymer electrical output and utilizing it via a compensating network operative to produce an output which is the square root of the products of inputs from the two sets of electrodes to precisely alter the amplifiers drive into the polymers first set to thereby maintain a desired constant acoustic output.

Abstract: A DTMF generator includes a high gain differential amplifier having a noninverting input, an inverting input, and an output. A first audio oscillator connects to the inverting input of the amplifier via a first series of frequency determining components. A second audio oscillator connects to the amplifier output via a second series of frequency determining components. The noninverting input of the amplifier connects to ground. A plurality of SPST switches interconnects the first and second frequency determining components, such that when any particular switch is closed, a unique feedback path is established from the amplifier output to the inverting input. This causes a ground potential to exist at the contacts of the particular closed switch thereby forcing both oscillators to turn on.