Midian's VPU series of inversion voice scramblers protect your voice communications against casual listeners. By mixing the frequency of the voice with an inversion tone in a balanced modulator, sum and difference frequencies are created. A low-pass filter eliminates the sum and the difference is transmitted as "inverted voice". The "inverted voice" undergoes an identical process on the receiving end that reconstructs the voice.
Midian's VPU-15-HYT1 is compatible with inversion scramblers from Motorola, MX-Com, Transcrypt, and Selectone.