March 1956 Popular Electronics
Table of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
published October 1954 - April 1985. All copyrights are hereby acknowledged.
Jerry missed an opportunity to patent his capacitive
touch switch, the sort used to control everything from living room lamps to kitchen sink faucets. Untold
millions of dollars in royalties could have paid for his engineering degree at Parvoo University and
then used the rest as seed money for a startup business. When I started reading the adventure of Carl &
Jerry, I thought they were going to rig the metal door to issue a high voltage pulse to whatever touched
it, but that probably would have been too much of a liability for Popular Electronics to risk since
readers would sometimes replicate the devices described in the articles.
Carl & Jerry: Electronic Trap
By John T. Frye
... It must have been around two o'clock in the morning when Jerry was awakened by
the light that winked on and off a few times in his face and then shone steadily.
"What are you doing?" Carl demanded lazily, as he turned over on his side on the leather couch to,
watch his chum, Jerry, who was busily twisting .the knobs of a small box sitting on the basement laboratory
"Deciding whether to take French or Spanish next year," Jerry answered curtly, as he continued to
adjust the dials.
Carl heaved his lanky frame erect and strode over to the bench.
"It sounded just as if you said you were deciding whether to take French or Spanish next year," he
said laughingly, and peered curiously through his horn-rimmed glasses at the little cabinet studded
with knobs, switches and a small meter.
"That's what I did say."
"Then you've flipped your wig for sure. I suppose you just say: 'Black box, black box, on the bench,
Which shall I take: Spanish or French?' and then this electronic understudy for the Delphic oracle
mulls it over for a few micro-seconds and comes up with the right answer."
"That's not too far off," Jerry said, with a grin on his round face. "This thing is the 'Decision
Meter' described back in October, 1955, Popular Electronics. You can read the article for yourself,
but briefly the gadget works like this: when these five dials, which operate potentiometers, are all
set at zero, zero voltage appears across this meter. Turning a knob in a counterclockwise direction
applies an increasing negative voltage to one terminal of the meter; turning the knob in the opposite
direction applies an increasing positive voltage. I arbitrarily assigned negative values to arguments
for French and positive values to arguments in favor of Spanish. As each point came to me, I turned
one of the knobs to right or left in accordance with whether Spanish or French was favored by that particular
consideration. How far I turned the knob depended upon how important the consideration was. Finally,
when all the arguments had been recorded, the instrument automatically and electrically summed up the
influence of all the knob settings, and showed by the way the meter was deflected whether Spanish or
French was favored. As you can see for yourself, for me personally, Spanish was indicated the better
"Well blow my fuse!" Carl exclaimed.
"Imagine us having an electronic brain!"
"That's what it really is, in a modest sort of way. Say, Carl, I want to show you something," Jerry
said suddenly, and he went over and opened the cellar door leading to the outside. "See these bad scratches
on the outside of the door? Pop is pretty steamed about them. He thinks Bosco is doing it, and he says
- and I quote - 'Either Carl's got to put boxing gloves on that mutt or give him a close manicure before
we have the house repainted this spring' - unquote."
"Bosco wouldn't do a thing like that," Carl denied hotly, getting down on his knees to examine the
scratches closely. "In the first place, he's too lazy to scratch that hard."
"Well, I'm neutral, but I have an idea how we can find out what's doing it."
As he finished speaking, Jerry dived into the large junk box beneath the bench and came up with a
small dusty chassis bearing two tubes, a couple of knobs, and a relay.
"What's that nasty-looking thing?" Carl asked suspiciously. "I'm not going to have Bosco hurt."
"Don't worry. I'm as fond of that animated flea-garage as you are. This is a capacity relay that
will let me know when anything gets close to that door during the night. I built it according to an
article that appeared in the very first Popular Electronics back in October, 1954."
"How does it work?"
"A sensing wire fastens to this binding post which is connected to the grid of the triode section
of the 12SQ7 tube. This triode section is hooked up as an r.f. oscillator. Some of the r.f. voltage
produced by the oscillator is rectified by the diodes of the 12SQ7, and this d.c. voltage is applied
as negative grid bias to the 50L6 tube - which has a sensitive relay in its plate circuit. As long as
the oscillator is operating strongly, a high bias is produced and the plate current of the 50L6 is low,
allowing the relay to stay open. However, if any living thing or large metallic object approaches the
sensing wire, the capacity between that object and the wire provides a path through which some of the
oscillator energy is drained off. As the oscillation weakens, so does the negative voltage produced
by the rectifying diodes. This decreasing negative bias causes the 50L6 plate current through the relay
to climb, closing the relay. The closing contacts can turn on a light, ring a bell, or operate any other
While talking, Jerry had been installing a short sensing wire along the door jamb and connecting
a light bulb, so that it could be turned on and off by the relay contacts. After carefully adjusting
the sensitivity controls of the capacity relay, he could cause the light bulb to turn on simply by walking
within three or four feet of the door. When he stepped back again, the light would go out.
"Now I'll feed this light current through the relay contacts into the pair of wires I have going
up to my bedroom," Jerry explained; "and whenever anyone or anything comes close to this door, it will
automatically turn on the light up there. That will wake me, without disturbing anyone else, and I can
sneak down here and discover Old Scratch - whatever he is-right in the act."
"It sounds just goofy enough to work," was Carl's comment as he started for home. He could not resist
waltzing back and forth across the threshold a couple of times to make the light blink on and off before
he started climbing the steps that led up to the yard level.
Quietly, he slipped into his bathrobe and soft-soled slippers, and started for the basement laboratory.
When he reached the door that led from the furnace room into the laboratory, he stopped short at the
sound coming from the outside laboratory door. It was not a scratching sound. Instead, it sounded more
as though some heavy metallic object was being run up and down the edge of the door.
"I always knew old Bosco was plenty smart, but I never thought he knew how to use a crowbar," Jerry
marveled to himself.
At that instant there was a sort of crunching sound, and the door swung open. Jerry waited only long
enough to see the tall outline of a man step inside and start probing the workbench with the narrow
beam of a flashlight held in his hand; then the boy fled silently up the stairs behind him. When he
reached the kitchen at the top of the stairs, he debated briefly as to whether or not he should go on
upstairs and try to wake up his father; but as he recalled how hard that worthy was to awaken, and how
panicky his mother was likely to become, he quickly decided against this. He moved silently into the
den and lifted the telephone receiver from the cradle. Silently he gave thanks to his scoutmaster for
making every boy in the troop memorize the numbers of the fire department, the police department, and
a twenty-four hour ambulance service. Using only his sense of touch, he fumblingly dialed the number
of the police department. Although the dial mechanism was really very quiet, its whirring sounded like
the grinding of a concrete mixer to the frightened boy - in fact, it made almost as much noise as his
"Police department, Sergeant Anderson speaking," a drawling voice came from the receiver.
"This is Jerry Bishop at 1810 Spear Street.
A burglar just broke into our outside basement door on the west side of the house and is prowling
around here somewhere right now. Come quick," Jerry whispered hoarsely into the mouthpiece that he was
wearing almost like an oxygen mask.
The voice that answered was crisp and businesslike, with all the drawl gone from it: "I gotcha, kid.
Don't get in his way. Just lay low. Our squad car will be there in a few seconds. Don't try to answer.
He may hear you. Just hang up and make yourself scarce until we get there."
Jerry tried to replace the receiver softly in the cradle, but at the moment of contact it chattered
against the base with a rattle like that of castanets. Holding his breath, Jerry stood there in the
dark listening intently. For a few long seconds he heard nothing except the pounding of his heart; then,
very softly, there was a familiar creak of the basement stairs. The burglar was coming up to the first
floor. Peering through a crack in the door of the den, Jerry could see a suffused glow of light on the
For the next few minutes - which seemed like hours - the boy used his knowledge of the house to keep
out of the way of the prowler, who quietly but systematically went about ransacking the whole downstairs.
Whenever he found something to his fancy, he chucked it into a burlap sack he carried over his shoulder
in true comic-book-burglar fashion. Since he moved very slowly and deliberately, it was not hard for
Jerry to keep him in view, without being seen himself. At one time the boy thought he heard the sound
of a distant car motor, but he could not be sure. He was concentrating so hard on keeping out of the
way of that probing flashlight beam that he had scant time to notice anything else.
Suddenly, as the man stood at the bottom of the stairs, a light was turned on in Jerry's room at
the head of the stairs. It flickered on and off a couple of times and then went out; but at the first
flicker the burglar had switched off his flashlight and moved swiftly toward the kitchen and the stairs
leading down into the basement. Jerry, confident that the flickering light from his bedroom had been
caused by the police coming through the outside door of the basement, followed warily. Just as he reached
the head of the basement stairs, the furnace room below was flooded with light and two policemen with
drawn revolvers faced the burglar standing in the middle of the floor.
"Don't move," the tall, lanky policeman commanded. His short, stout partner moved forward and placed
a pair of handcuffs on the wrists of the burglar, whose mouth still gaped open with surprise.
"Boy, am I glad to see you guys!" Jerry exclaimed, thumping down the cellar steps. "Those brass buttons
on your uniforms look prettier to me right now than any Christmas tree ornament I ever saw!"
"Now there's a heartfelt testimonial," the tall policeman chuckled; "but while the compliments are
going around, you've got some coming for keeping cool and using your head. How did you happen to - "
He broke off sharply as strange sounds issued from the adjoining laboratory. There was a scratching
at the outside door accompanied by a faint clicking that Jerry recognized as coming from the relay in
the capacity-operated unit.
"Sh-h-h! Maybe it's an accomplice," the lanky policeman said, as he moved swiftly across the laboratory
to the door and stood poised before it with his revolver tightly clenched in his fist. He jerked the
door open and sprang to one side all in a single motion. There in the doorway - with one paw still raised
to scratch the disappearing door - stood Bosco, a look of doglike astonishment in his brown eyes. Then
he recognized Jerry, and his stubby tail began to vibrate at about sixty cycles per second.
"Come on in, you old rascal," Jerry ordered; then he dropped on his knees and hugged the shaggy dog
with almost hysterical affection. "You got caught in the trap, all right, but when Dad hears that because
of you we caught a burglar, maybe he won't worry too much about a few little scratches on the cellar
Posted February 15, 2017
Carl & Jerry: Their Complete Adventures is now available. "From
1954 through 1964, Popular Electronics published 119 adventures of Carl Anderson and Jerry Bishop, two teen boys with
a passion for electronics and a knack for getting into and out of trouble with haywire lashups built
in Jerry's basement. Better still, the boys explained how it all worked, and in doing so, launched countless
young people into careers in science and technology. Now, for the first time ever, the full run of Carl
and Jerry yarns by John T. Frye are available again, in five authorized anthologies that include the
full text and all illustrations."
Carl & Jerry Episodes on RF Cafe
- Electronic Eraser,
- Electronic Trap, March
- Geniuses at Work, June
- Eeeeelectricity!, November
- Anchors Aweigh, July
- Bosco Has His Day,
- The Hand of Selene,
- Feedback, May 1956
- Abetting or Not?, October
- Electronic Beach
Buggy, September 1956
- Extra Sensory
Perception, December 1956
- Trapped in a Chimney,
- Command Performance,
Education, July 1963
- Treachery of Judas, July
- The Sucker, May 1963
- Stereotaped New
Year, January 1963
- The Snow Machine, December
Education, July 1963
- Slow Motion for
Quick Action, April 1963
- Sonar Sleuthing, August
- TV Antennas, August 1955
- Succoring a Soroban,
- "All's Fair --", September
- Operation Worm Warming,
- The Blubber Banisher,
- The Sparkling Light, May
- Pure Research Rewarded,
- A Hot Idea, March 1960
- The Hot Dog Case, December
- A New Company is Launched,
- Under the Mistletoe,
- Electronic Eraser,
- "BBI", May 1959
- Ultrasonic Sound Waves,
- The River Sniffer, July
- Ham Radio, April 1955
- El Torero Electronico,
- Wired Wireless, January
- Electronic Shadow,
- Elementary Induction,
- He Went That-a-Way,
- Electronic Detective,
- Aiding an Instinct,
- Two Detectors, February
- Tussle with a Tachometer,
- Therry and the Pirates,
- The Crazy Clock Caper,