I am not sure of the origin of this circuit. This is an item that came from my files.

The lattice circuit can be used to mix two signals into one or split one signal into two. There is complete isolation between the split signals (shown on the left in the diagram below). Shorting one input will not affect the other input.

This circuit is ideal for encoding and decoding matrix stereo signals. It is suitable for any application where a passive function is required and the resulting loss in signal level is not important.

Chriss Scherer
editor, Radio magazine

This can be used as a passive mixer or splitter. Either way, there is complete isolation between each input. Resistors should all be of the same value and will determine the input and output impedance. For a 600 ohm circuit input and output impedance, use 600 ohm resistors. For a 10k ohm impedance, use 10k ohm resistors. Loss through the device is always 6dB.