anr
I know it’s a different Mk of aircraft, but this may be of interest, given it is a safety issue.
DESIGN, MANUFACTURE & SUPPLY OF ACTIVE NOISE HEADSET INTERFACE BOXES AND CONNECTING LEADS
Summary of Requirements:
The Nimrod IPT has a requirement for the Design, Manufacture and Supply of a replacement Active Noise Reduction (ANR) Headset Interface Box and its Connecting Leads, for use on the Mission System of the Nimrod R Mk1. The box is to be designed to the same size restraints as the existing Headset Interface Box, but is to include provision for the ANR Power Supply to be feed through the box by the addition of extra connectors. The replacement box is required to be new build.