MQS-34 A/B-Signal Switch works two ways. It lets you switch a common source signal (guitar, bass or keyboard) between two amplifiers or amp channels. Or conversely, it lets you switch two source signals (eg, two different guitars) into the same amplifier.A good quality A/B-Y switcher will also provide LEDs or other indicators to show whether A, B or Y routing is in effect. The Yrouting combines both the A and B outputs in parallel so that amplifier can be driven at once.