An arrangement for grouping multiple television channels for recording is presented. A first reference array and a second reference array are fabricated on the memory core such that a reference cell pair comprising one cell of the first reference array and a corresponding cell of the second reference array are read and averaged to provide a reference voltage for reading a data array. A pivotal mulch door is located within the exit tunnel with the mulch door swinging between two positions. The sampling device comprises a DC sampling voltage source, a threshold sampling circuit, a photoconductive switching element and a light source. The tool may optionally include a feature that indicates to an operator the spray pattern orientation. The curable composition produces a cured product that does not show coloration even when exposed to high-energy light or subjected to a high temperature, exhibits excellent transparency for a long time, and has high adhesion even at a high temperature.