A cylindrical magnetic stylus driven by a coil can be used to transfer bits of information onto a magnetic surface. These bits are recorded as round spots and combinations of these spots can form a desired pattern, e.g., numbers or letters. A mathematical model corresponding to the magnetic properties of a recorded spot is proposed and analyzed. The major considerations in the analysis are the field pattern existing about the spot, the self-demagnetization of the spot, and interference resulting from crowding the spots. Field mappings, obtained with a miniature Hall probe, were used to experimentally verify the proposed model. The experimental results show that the analytic model can predict the magnetic configuration of the spot at distances away from the recording surface that are considerably greater than the surface thickness. An alternate model is proposed for studying spot properties in regions quite close to the recording surface.

A step-by-step procedure is presented for formulating circuit synthesis problems in a manner amenable to solution using linear programming. A method of systematizing component value determination using linear programming is explained. The design equations and conditions required to synthesize a diode-coupled inverter and a design procedure for achieving an optimum circuit are presented. The Simplex Method is used to determine component values such that power dissipation is minimized.

The concept that the junction transistor is a charge-controlled current source is reviewed. Saturated operation and non-saturated operation are defined on the basis of minority and majority carrier distributions in the base region. Several common emitter switching circuits are analyzed. The switching efficiency, a figure of merit based on the charge storage properties of the transistor, is introduced. Saturated and nonsaturated operation are compared on the basis of switching efficiency, transient waveforms, stability of the voltage levels, power dissipation, noise rejection and suppression ablity, and circuit complexity. Currently-used antisaturation techniques are discussed.