Comprehension: A Personal Experience in Content Area Reading.
George Manolakes · The Reading Teacher · 1988
200 The Reading Teacher December 1988 diagrams. It seemed simple enough for any 10 year old to read! Here are three paragraphs from this ar ticle (Forman and Nawracaj, 1966): How It Works The scope calibrator is basically a simple solid state astable multivibrator designed to close toler ances. Transistors Q2 and Q3 comprise the multivibrator, whose frequency is determined es sentially by the values of the timing components Cl, C2, R3 and R4. The nominal 1020-Hz fre quency can be reduced to an exact 1000-Hz signal by merely shunting Cl and C2 with a 20-pf. capac itor. Emitter follower Q4 serves to isolate the mul tivibrator from the load effects of the output circuit while functioning as an impedance-matching de vice. Transistor Ql serves only as a battery condi tion indicator. It is employed in an emitter follower configuration with a 10-volt lamp (II) serving both as an indicator and as the emitter resistor. As the source battery deteriorates, its output gradually approaches the zener (Dl) voltage, re ducing Ql's base bias and thus causing the lamp to glow more and more dimly. This can be observed by pressing the battery test switch (S2). However, because the calibrator would normally be used only on occasion rather than continuously, the life of the battery can be expected to approach its no-use shelf-life.