Transistor circuits for magnetic drum recording

Drum recording is accomplished bypassingcurrent through a magnetically soft write head placed in close proximity to a magnetically hard drum surface. Flux from the head resulta in magnetized areas on the drum surface. Drum coatings and heads presently in use require writing currents in the order of 1 ampere. Head impedances are typically 2 to 5 ohms. This means the writing circuit must supply severa! watts of power. The use of the following three basic circuits is outlined: power one-shots, bloc king oscillators, and class B amplifiera.