Number of slots
For a block horn: the number of slots machined into a specified surface. A horn would typically be described by the number of slots in two adjacent lateral surfaces — e.g., if a width surface has 4 slots and a thickness surface has 2 slots, then the horn would be described as a "4‑slot x 2‑slot" horn. The total number of slots is the number of slot openings on two adjacent lateral surfaces of the horn — in the previous example, 6 slots.
For a cylindrical horn with cross slots: one-half the number of slot openings on the cylindrical surface of the horn. (This agrees with the number of cross slots in a block horn, since the cylindrical horn may be derived by machining a block horn.)
For a cylindrical horn with radial slots: the number of slot openings on the cylindrical surface of the horn.