The Model 721 is a modular two-channel rack mounted lowpass filter. Each module contains two independent signal channels. One of five frequency cutoffs,or filter bypass, is selected with a front panel rotary switch for each channel. The Model 721M adds switch-selectable gain of 1, 10, or 100.

The Model FL724 notch-reject filter can be configured for up to 55dB of signal rejection at 60Hz or 50Hz. The unit operates from a ±15VDC, 25mA regulated power sourcewhich is available as a matching module (Model FL854).