excellent animated study of the H2S indicator unit
and switchbox Type 207B. The vast Navigator's section covers all items
of equipment used along with in-depth studies and colour diagrams
covering the AMI Mk.I, API Mk.I, GPI Mk.I, Astrograph Mk. 1a, GEE
Mk.IIB, H2S System along with SBA Beam Approach systems. The Navigators
tour also offers over 110 superb colour full screen photographs and
covers the smaller items of equipment, such as the 'Douglas' used
by the 'Nav' during operations.