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January 1966 Radio-Electronics

January 1966 Radio-Electronics

January 1966 Radio-Electronics Cover - RF Cafe[Table of Contents]

Wax nostalgic about and learn from the history of early electronics. See articles from Radio-Electronics, published 1930-1988. All copyrights hereby acknowledged.
"What's Your EQ?, January 1966 Radio-Electronics - RF Cafe

Conducted by E. D. Clark

Two puzzlers for the students, theoretician and practical man. Simple? Double-check your answers before you say you've solved them. If you have an interesting or unusual puzzle (with an answer) send it to us. We will pay $10 for each one accepted. We're especially interested in service stinkers or engineering stumpers on actual electronic equipment. We get so many letters we can't answer individual ones, but we'll print the more interesting solutions-ones the original authors never thought of.

Write EQ Editor, Radio-Electronics, 154 West 14th Street, New York, N. Y. 10011.

Answers to this month's puzzles are on page 101.

How Many Relays?

Using ordinary spst switches, working from any toggle standard type of power, how many relays can you control on the far end of this shielded two-conductor line, each entirely independent of all others? -Eugene Austin

Glow-Lamp Memory Circuit

This flip-flop memory circuit uses two NE-23 neon glow lamps and a 30:1 audio output transformer that functions as a voltage-peaking transformer. The output is in the form of transient peaks that exceed 45 volts and are sufficient to fire a nonconducting lamp.

When the circuit is stable, one lamp is on and the other is off. The voltage requirements of NE2 are: firing voltage 75, maintaining voltage 65, and extinguishing voltage 64. NE1 has a firing voltage of 70, maintaining voltage of 60 and extinguishing voltage of 59.

The push buttons (S1, S2) are normally open and each is correlated to a glow lamp. When a button is pressed, the lamps will flip. Upon release, they will flip. Can you determine which lamp will flip into steady conduction if S1 is pressed for 1/2 second and released? -Kendall Collins

 

Quizzes from vintage electronics magazines such as Popular Electronics, Electronics-World, QST, Radio-Electronics, and Radio News were published over the years - some really simple and others not so simple. Robert P. Balin created most of the quizzes for Popular Electronics. This is a listing of all I have posted thus far.

RF Cafe Quizzes

Vintage Electronics Magazine Quizzes

Vintage Electronics Magazine Quizzes

Vintage Electronics Magazine Quizzes

These are the answers. Puzzles are on page 58.

How Many Relays?

Four relays can be controlled, as shown in the diagram. If only S1 is operated, pulsating dc is put on the line. The polarity is such that current passes through the rectifier to RY1, but is blocked from RY2 by its rectifier. The cable shield serves as return for all control circuits.

If only S2 is closed, pulsating dc of the opposite polarity is put on the line, passing through the rectifier to RY2, but blocked from RY1. If both S1 and S2 are operated, ac is put on the line, operating both RY1 and RY2.

The same sequence holds for S3-RY3, and S4-RY4. The capacitors connected across the relay coils eliminate chatter.

Glow-Lamp Memory Circuit

Assume NE1 is conducting and potential at point A is +60 volts - the maintaining voltage of NE1. When S1 is pressed, the transformer produces an output pulse of +45 volts (or more). This causes the circuit to flip. The pulse passes through NE1, raising the potential of A to a peak that fires NE2. As the output-pulse voltage falls toward zero, N1 is extinguished and N2 remains conducting

When S1 is released, a negative output pulse of -45 volts (or more) is induced in the transformer secondary. This causes the circuit to flop by firing NE1. As a result, A is clamped at +60 volts and NE2 is extinguished.

If NE2 is initially conducting, the positive output pulse does not switch NE1 into steady conduction. However, the succeeding negative output pulse causes NE1 to flop into conduction and, as a result, NE2 is extinguished.

A positive pulse of sufficient duration (produced by S1) always flops NE1 into steady conduction. Conversely, a negative S2 pulse of sufficient duration always flops NE2 into steady conduction.

Note: An approximation of the output waveform can be obtained by modifying the input circuit (one polarity) as shown in the diagram. Otherwise, when the button is released, the output-pulse amplitude is much greater than when the button is pressed. This is caused by the higher speed of field collapse in the transformer as compared to build-up. The diode simulates a low-impedance zero source when button is released.

 

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RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while tying up your telephone line, and a lady's voice announced "You've Got Mail" when a new message arrived...

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