2-Way Stereo Amplifier Speaker Selector, AB Speaker Switch 2 Zone Distribution
For use w/ 8-16 ohm impedance speakers. A21 is an amp switcher/speaker switcher. You can choose 2-IN-1-OUT for 2 amplifiers to 1 pair of speakers, or in reversible direction of 1-IN-2-OUT for 1 amplifier to 2 pairs of speakers.