A versatile and flexible summing amplifier for airborne audio systems.

The P178 Fail-Safe Audio Mixer is an 8-input mixer providing 3 composite outputs. Channel 1 and Channel 2 Composite Outputs are Failsafe Relay Protected for Master Caution or Essential Tones to ensure that no fault in the system or an electrical bus failure can prevent pass through of Essential Warnings or Tones. Channels 3 through 8 are for non-essential tones and will drop offline in case of fault or Avionics Bus failure.

The P178 also removes the need for external relays, ensuring that essential tones are passed to unswitched inputs on any audio system. The unit also has internal fault detection. Upon fault, the relays go to their normally closed (Failsafe) position. The Fail-Safe Audio Mixer also has a pull low line on fault if an external fault indicator is desired.