A hollow wooden sounding box 1290 x 130 x 110mm provided with scales divided in millimetres between fixed bridges over which the wires are stretched. A spring balance reading 100N x 5N is fitted to one end and the tension exerted and measured can be finely adjusted by a wing nut. Another wire passes over a pulley and can be loaded as desired. A third wire is provided for comparison, its tension may be adjusted by means of a wrest pin. Supplied with anti-corrosive steel wires. The distance between the fixed bridges is 720mm. Complete with three movable bridges, wrest pin key and a set of four 1.5m wires 20, 22, 24, 26 swg without weight.
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