Abstract: An apparatus for storing unused felt pens for use in an electronic input board system includes a plurality of pen loaders. In systems in which multiple color information is written on the electronic board, colored felt pens are provided and one of these color felt pens is replaceably mounted in a pen holder. In order to prevent drying out of ink, the unused felt pens are sealed with a cap which is positioned within each pen loader. When a felt pen is loaded into the pen holder to write a letter or a graphic pattern of a selected color, a switch detects which felt pen has been selected for loading in the pen holder, and the system identifies the color of the pen. The apparatus maintains the points of unused felt pens airtightly sealed within the cap to protect them against drying out of ink, while allowing a single-handed operation for loading/unloading a felt pen into/from the pen holder without staining the operator's fingers, clothes, etc. with ink.

Abstract: A magnetic recording head, a resistor, a capacitor and another resistor are connected in series to form a bridge circuit arranged to satisfy the condition Ra.multidot.Rb=L/C, wherein Ra and Rb represent the resistance values of the resistors, respectively, L represents the inductance value of the magnetic recording head, and C represents the capacitance value of the capacitor. A recording signal is applied across a first pair of opposite junctions of the bridge circuit, and an AC biasing signal to be used in recording the recording signal is applied across a second pair of opposite junctions of this bridge circuit.

Abstract: A single magnetic head assembly having vertically stacked separate units of recording and playback cores is comprised of a first unit of at least one recording cores, and a second unit of at least one playback core which is located in stacked positional relationship relative to the first unit. These units of cores are arranged to be jointly shifted vertically to meet the required track of the magnetic tape when used, to thereby utilize that particular unit of cores optimum for recording or playback, as desired.

Abstract: An audio power amplifier can be operated in either class A, class B or class AB amplifier modes by selectively switching bias values set in a bias setting circuitry provided for a driver stage which drives the main power amplifier stage.