Abstract: An improved light-exposure control unit for a photographic printer offering minimized leakage problems, elimination of special precision capacitors and a range selecting circuit which eliminates masking of the photosensitive device used to detect variations in intensity of the light source. The improved control unit including operational amplifiers connected to the photosensitive device, which is mounted after the color filter but before the negative, sending a voltage adjustable according to the desired range and proportional to the amount of light impinging thereon, to an integrating amplifier with a variable input resistance adjusted accordingly to the desired density. The integrating amplifiers output is compared to a voltage derived from a precision reference source adjustable according to the settings made to magnification and speed-factor controls.

Abstract: A gated electronic metronome including an oscillator generating pulses for a counter that divides them to the fundamental tempo which is gated with a switch-selectable binary division of the fundamental tempo to produce an interrupted pattern of the fundamental tempo so a singer, player, drummer, etc. can monitor the error in his or her ability to maintain tempo without a reference.