Comprises U & I cores of low loss magnetic material, to form a closed core of cross section 25 mm in plane of laminations, 32 mm perpendicular to them is an I - core of length 102 mm. U core external height 102mm. Internal height to take bobbin length 77 mm. Pair of pole pieces, each 65x30x25 mm with on end shaped to part of a cone for maximum flux density. Hole drilled through total length along cone axis to take a light beam. Pole pieces will accept supertrods & shading ring (provided with accessories) & may be clamped on any separation on U core, or in contact as a non laminated I - core. Cast aluminium alloy stand consisting of a heavy base on four rubber feet with removable clamping arms. Maximum dimensions of base 190x200x115 mm. Channel 35 mm wide & 3 mm deep to take transformer core, extends across full width. Integral support for arms, to rear, is below the level of the pole pieces. Arms pivot on steel spindle with adjustment of knobs to rear bringing hard rubber pads at front end of arms to bear on transformer core. Synthetic hammer finish except of clean metal in channel & 4 mm hole to take on earthing plug lead. Complete with all the accessories.