The STD series of products is part of the STICK-ON line of products from Radio Design Labs. It is a resistive branching network with RF filtering on each of the four channels. Any channel, A through D, may be either input or output. This permits combining stereo signals into mono inputs, splitting mono signals to multiple inputs, and even combining microphones with output shorting switches into a single amplifier input. The STD products are available in 150 ohm, 600 ohm and 10 kohm models. All inputs and outputs are balanced.