|Horn and photos courtesy Ron Chamberlain.|
The A-6 was intermediate in size between the A-2 and B-6 single-note Wabco horns. Similar in overall appearance, these three types of horns can be distinguished by the treatment of the nuts on the front of the power chamber: A-2 horns have no exposed nuts, A-6 horns have the nuts slightly raised, and B-6 horns have the nuts slightly recessed. There are also differences in the pattern of the reinforcing ribs on the sides of the horn bells.
Information is lacking on the bell sizes and frequencies available with the A-6, though evidently no twin chime version was ever manufactured. The fundamental of the horn that produced the samples below is 310 Hz, or roughly D#.
Use of the A-6 on locomotives is likewise not well documented. Wabco did specify the A-6 in a number of 24-RL air brake system diagrams published in the 13th, 14th, and 15th editions of the Locomotive Cyclopedia of American Practice (1947, 1950, and 1956), either paired with an E-2 on A-units or by itself as the hostler's horn on B-units. In practice, it appears cab units with Westinghouse horns more frequently had pairs of E-2's. Alco PB-1 boosters often had a single, small Wabco horn on the roof, but are seldom photographed closely enough to distinguish an A-6 from a similar-looking A-2 or B-6 horn.
A-6 sound samples:Courtesy Ron Chamberlain: