In practice, 1105, 1106, 1107, 1108 and storage means 1214 may be functional parts of a personal computer, such as a laptop or similar. 1105 and 1106 may be within a headstage. [0081]FIG. 12 shows the block diagram of a preferred form of the BRM. (The drawing is presented in two sections, joined by a row of connectors at (A)-(E); and for simplicity depicts a single channel although two are actuall