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What's Your EQ?
September 1966 Radio-Electronics

September 1966 Radio-Electronics

September 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.

Three more "What's Your EQ?" circuit problems await your solutions here. They appeared in the September 1966 issue of Radio-Electronics magazine. Most of these circuit analysis / design challenges are timeless in that successful completion does not require an in-depth knowledge of components of yesteryear. Usually, when something like a vacuum tube, neon lamp, or selenium rectifier shows up, you can take a reasonable stab at the answer just by looking a the circuit, or thanks to the readily available knowledge base of the Internet, discover what you need pretty quickly. The vast majority of the circuits involve only resistors, capacitors, inductors, transformers, lamps, diodes, and switches. Such is the case this month. Bon chance.

What's Your EQ?

"What's Your EQ?, September 1966 Radio-Electronics - RF CafeThree puzzlers for the student, theoretician and practical mono Simple? Double-check your answers before you say you've solved them. If you have an interesting or unusual puzzle (with on 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.

Conducted by E. D. Clark

Remote-Control Circuit

Using 60-Hz current and single-pole switching, how many independent relay-controlled circuits can you operate from a two-conductor line? Only one load circuit is energized at a time.

- E. A. Johnson

 

Bridge Resistance - RF CafeBridge Resistance

The diagram shows the familiar bridge circuit. What value will the ohmmeter read with S1 open? With S1 closed?

- Joseph Kish Jr.

 

All 1-Ohm Black Box - RF CafeAll 1-Ohm Black Box

The black box in the diagram has 9 terminals. Using only 9 resistors (same value), how can one connect them in such a way as to have a value of 1 ohm appear between any two terminals?

- Robert G. Donnell

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

Answers to What's Your Eq?

These are the answers. Puzzles are on page 53.

Remote-Control Circuit Solution - RF CafeRemote-Control Circuit Solution

With the switch in position 1, only RY1 is energized (via D1 and D2). In position 2, only RY2 is energized (via D3 and D4). In position 3, ac is fed to the line, energizing both relays. In position 4, neither relay is energized. Since there are four different combinations, appropriate contacts may be selected to operate four independent circuits.

By duplicating this setup and using a three-conductor line (add a shield), six independent circuits may be controlled. (Fig. 2) The switch position in which neither relay is energized is eliminated as is one auxiliary relay. Otherwise, it is possible to have two load circuits energized simultaneously.

Bridge Resistance Solution - RF CafeBridge Resistance Solution

The ohmmeter reads 10,000 ohms in both switch positions. As shown redrawn with S1 open (Fig. 1), the meter sees the four resistors in series-parallel-two 20K series legs in parallel totaling 10K.

With S1 closed (Fig. 2), the meter sees R1 and R2 paralleled to 5K in series with R3 and R4 paralleled to 5K for a total of 10K.

All One-Ohm Black Box Solution - RF CafeAll 1-Ohm Black Box Solution

Simply connect one end of each 112-ohm resistor to a different terminal and connect the 9 free ends together.

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About RF Cafe

Kirt Blattenberger - RF Cafe Webmaster

Copyright: 1996 - 2025
Webmaster: Kirt Blattenberger,
   BSEE - KB3UON - AMA92498

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...

Copyright  1996 - 2026

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