BITE Compatibility and Legacy Systems

A feature of our Long Life Jacks is the inclusion of "shunt", or switching terminals. When a headset plug is removed from the jack, the signal terminals make a connection with a second set of terminals.

This can be utilised in two ways:

1. Legacy System Compatibility
   Some older systems were designed with an audio output impedance of 300 Ohms. Because of the nature of their design, it is important that these systems are presented with this load at all times - even when the headset is not plugged in.
   If the audio jack does not include shunt terminals then it may not be suitable for use with Legacy systems, as the audio output will be presented with an open circuit when the headset is removed.
   
   Customers should check to see if "Shunt" terminals are required before specifying their Audio Jacks.
   
2. BITE Compatibility
   The inclusion of shunt terminals within an audio jack provides an opportunity for remote testing of the audio jack module using the IFE system BITE (Built In Test Equipment). By making use of the secondary electrical circuit when the headset plug is removed from the jack, a simple electrical check can be undertaken by passing a test current between the seat box and the jack. This saves the time and effort of checking each seat individually for audio using a headset, and allows a whole aircraft to be tested within a matter of seconds.