February 1958 Popular Electronics
of Contents]People old and young enjoy waxing nostalgic about and learning some of the history of early electronics.
Popular Electronics was published from October 1954 through April 1985. All copyrights (if any) are hereby acknowledged.
Long before their college days at Parvoo U., our two amateur electronics
sleuthing buddies were on the job tracking down and trapping bad
guys by using their combined knowledge of circuits and physics.
In this episode, Carl and Jerry are tasked with helping a hobby
store owner stop a rash of thefts that always seems to occur during
a busy time right after school lets out for the day. Their first
inclination was to devise a system like the big department stores
were installing that used passive tags on items that would trigger
an indicator when passed through the detector at the exit door.
That was in 1958 (the year I was born, yikes!)
when the anti-theft tags were first being utilized. Unfortunately,
the system they were able to build was not sensitive or selective
enough, so they came up with a different scheme that helped the
storekeeper nab the perp. It was quite elementary, as a world-famous
detective was fond of saying.
See all articles from
Carl & Jerry: Electronic Detective
By John T. Frye
February snowstorm was swirling around outside as Carl Anderson
came stamping into the basement laboratory of his friend, Jerry
Bishop. His horn-rimmed glasses instantly steamed over in the warm
room, and when he took them off he saw that Jerry had company. A
pleasant-featured young man was sitting on the worn leather sofa
watching Jerry doing something at his workbench.
"Hi, Carl; this is Mr. Singer who owns that hobby shop at Fifth
and High," Jerry announced. "He's got a problem."
"Glad to know you, Carl," Mr. Singer said, as he stood up and
shook hands. "I've got a problem all right. Shoplifters have really
started working me over. As you know, our merchandise is mostly
on open display so that the youngsters who make up a large part
of our trade can handle it. That makes it easy picking for anyone
so inclined. Naturally we expect some losses of this nature, but
recently they've become serious."
"What sort of things are snitched?"
"Everything from a bicycle on down!
However, that fancy cap pistol Jerry has over there on the bench
seems to be a favorite. We've lost a couple of dozen of those since
"Then it must be children doing it." "That's right; and that's
what makes catching the sticky-fingered person such a ticklish proposition.
Maybe I'm a softy, but I don't want to call the police in on this
and maybe send some kid to reform school. I just want to find out
who's doing it and put a stop to it. I feel I have to show the kid
doing it that no-one gets away with what he's pulling for long;
otherwise he may develop into a real criminal."
"Don't you keep an eye on things?"
Everything was built on a flat sheet of Bakelite that
fitted easily beneath the cardboard shelf to which the pistol
was securely fastened.
"We try, but you can't appreciate what a job it is until you
see the after-school crowd that jams into our store. We have all
we can do waiting on trade, stopping scuffling, etc., without trying
to watch all the counters and aisle displays at once. And the thief
is pretty crafty. We thought we could stop the loss of the pistols
by wiring them in their boxes; but they kept right on disappearing,
box and all!"
"Carl, you're just in time to help me try something," Jerry interrupted.
"I read the other day that some big department store had installed
an electronic shoplifting detecting device that was triggered whenever
a special price tag, actually a miniature printed tuned circuit,
was brought near it. Price tags were removed from all merchandise
when sold; so if anyone tried to carry something off without buying
it, the electronic gadget would squeal on him.
"I figure the detecting device must be simply a glorified grid
dip oscillator such as the one I have here on the bench. As Carl
knows but possibly you don't, Mr. Singer, a 'GDO,' as we call it,
is simply a vacuum-tube oscillator with a meter that reads the rectified
grid current which flows from the tube grid to ground as long as
the tube is oscillating. The amount of grid current is proportional
to the vigor of oscillation. Whenever another circuit tuned to the
frequency at which the GDO is oscillating is brought near the coil
of the oscillator, this tuned circuit absorbs energy from the oscillator
by induction. This cuts down on the vigor of oscillation and produces
a reduction or 'dip' in the current reading of the meter."
"I see that this loop of wire strung around the door frame is
replacing the coil ordinarily plugged into the GDO," Carl observed.
"That's right. And this little coil-and-capacitor combination
is tuned to the frequency at which the grid dip oscillator is working.
I want you to walk back and forth through the door without it first
- then again with it in your hand."
As Carl made the last trip, Mr. Singer walked over and watched
"The pointer moved!" he exclaimed.
"Yes, but not enough I'm afraid," Jerry said. "I was hoping we'd
get a really strong kick that would operate a sensitive relay. And
there was a current change caused by body capacity effect when Carl
went through the loop without the tuned circuit. Probably we could
get away from that by housing the loop of wire in some sort of Faraday
shield which would stop capacity effects without interfering with
magnetic induction ... and we could amplify the grid current change
with a d.c. amplifier until it would kick a relay. But I'm afraid
all that wouldn't be practical for just this one job."
"Well, I'm sorry you can't help, but I certainly appreciate your
trying," Mr. Singer with obvious disappointment as he began buttoning
"Wait a minute!" Jerry exclaimed. "We don't give up that easily.
I've got another idea that should be sure-fire."
"Let's hear it," Mr. Singer said, sitting down again.
"Well, I've been looking at this cap pistol carton, and I see
there's plenty of room beneath the cardboard insert that holds the
pistol for us to conceal a transistorized, tone-modulated transmitter.
This will have a range of only about 50 feet; so if the pistol is
placed on a counter at the rear of your store, the signal won't
be heard on the receiver we'll place near the front door - with
an antenna lead from the receiver fastened around the door frame.
However, if anyone tries to carry the pistol and transmitter through
the door, the signal from the transmitter will be heard very loudly
in the receiver."
"Sure it will work?" Mr. Singer quizzed. "Sure I'm sure," Jerry
"Carl and I have played around with these transistorized wireless
mike circuits a lot, and we know how to build them and what they
will do. Suppose you don't display the cap pistols for a couple
of days while Carl and I build up the transmitter and check it out.
Then you can put this special one on display, and the kid pinching
them will probably snap it right up."
"That's exactly what I'll do," Mr. Singer agreed. "Just let me
know when you're ready."
The door had hardly closed behind him before Carl and Jerry were
busy laying out the little transmitter. There was no problem with
the circuit, for all they had to do was combine a transistorized
"wireless mike" transmitter and a simple transistorized audio oscillator.
The audio oscillator replaced the microphone of the transmitter
and modulated the output with a steady tone of about 500 cycles
per second. The transmitter was set to work on an unused area near
the low end of the broadcast band so that an ordinary radio could
be used to pick up the signal. Everything was built on a flat sheet
of Bakelite that fitted easily beneath the cardboard shelf to which
the pistol was securely fastened.
When the equipment was working to their satisfaction, the boys
contacted Mr. Singer; and that evening the three of them went down
to the store and set up "Elmer, the Electronic Flatfoot," as Carl
insisted on calling it. Everything worked exactly as Jerry had predicted.
It was agreed the boys would rush right to the store from school
the next day and that Mr. Singer would not put out the pistol until
It seemed as though school would never let out the next afternoon,
but when it finally did Carl and Jerry really hot-rodded their bikes
down to the store. Mr. Singer was waiting for them. Jerry switched
on the hidden transmitter, and the "bait" was provocatively displayed.
Almost immediately the store began to fill with a crowd of shouting,
shoving, noisy boys. Jerry and Carl stayed near the front of the
store and deliberately avoided even looking at the counter holding
the cap pistol. Mr. Singer, his wife, and two clerks were busy waiting
Removing the receiver from his shirt pocket, he used
it as a search wand to go over each one.
A good half hour passed without anything happening. The boys
were just beginning to think that no one was going to try to make
off with the pistol when they heard a weak musical tone in the receiver.
Steadily it increased in strength. Mr. Singer heard it and came
over to stand by Carl and Jerry. As two well-dressed boys carrying
school books went through the door, the tone reached a very loud
level and then began to subside.
Mr. Singer called after them: "Say, fellows, come back here a
minute. I want to talk to you."
The two schoolboys exchanged a long look and then slowly came
back to the store. As they crossed the threshold, the receiver once
more built up to a peak of sound.
"Come on back to my office," Mr. Singer said.
They walked back with him, tossing their books on an empty counter
as they went past. Carl and Jerry followed, and for the first time
Carl noticed that Jerry was wearing his little shirt-pocket transistor
receiver with its earphone tucked in his ear. Carl also noticed
that as Jerry walked along just behind the two boys he kept fumbling
with the tuning control of this receiver, and his face had begun
to wear a puzzled, worried look.
"I was going to use this to tell which one had it," he whispered
to Carl, "but I can't pick up the signal near either of them!"
"Maybe the transmitter's gone dead," Carl suggested.
"Nope, I can still hear it faintly on that receiver up front,"
Jerry observed as they reached the door of Mr. Singer's office.
"You tell Mr. Singer to stall," he said desperately, "while I see
if I can find what's gone wrong."
As the rest of them filed into the office, Jerry turned around
and started walking slowly toward the front of the store, tuning
his little receiver back and forth across the low end of the broadcast
band as he did so. Suddenly he began picking up the tone signal,
but after he had walked about two-thirds the length of the store
it began to fade out again. Backtracking, he found that the signal
reached a peak when he was standing by the books the boys had tossed
on the counter. He quickly spread the books out on the counter.
Removing the receiver from his shirt pocket, he used it as a search
wand to go over each of them. One large, fat volume on ancient history
gave out a very loud signal.
Jerry opened the book and made an astonishing discovery. The
first and last few pages of the book were intact, but the center
of all the middle pages had been cut out. Inside this opening was
the cap pistol still wired in its box.
He picked up the book and, holding it behind him, stepped into
"Which one of you boys is named William Palmer?" Jerry demanded.
The boy with dark auburn hair and freckles spoke up hesitantly:
"Then this must be your book with your name in the front of it,"
Jerry said quietly as he placed the book on the desk in front of
Mr. Singer and opened it.
The Palmer boy's face turned so deathly white that his freckles
seemed to stand out in three-dimensional style.
"I didn't really mean to steal," he stammered. "Honest, I didn't.
It just seemed a kind of game, and the other fellows kept egging
me on. Are - are you going to send me to jail?"
"Come on, Carl," Jerry said as he headed for the door.
Carl followed, but even after the door was closed behind them
Carl and Jerry could still see the pale frightened faces of the
two boys and the stern serious look on the face of Mr. Singer.
"What do you suppose Mr. Singer will do with them?" Carl wondered.
"I'm not sure, but it will be what's best for the boys," Jerry
declared with conviction. "They just don't know how lucky they are
that they were caught by a fine man like Mr. Singer. You can bet
he'll not let them off too easy. From the looks on their faces,
though, I think they've already learned their lesson."
"But they'll never know it was Elmer, the Electronic Flatfoot,
who put the arm on them!" Carl said with a grin.
Jerry: Their Complete Adventures is now available. "From 1954 through 1964, Popular Electronics published
119 adventures of Carl and Jerry, 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 Beach Buggy
- September 1956
- Extra Sensory Perception
- December 1956
- Trapped in a Chimney
- January 1956
- Command Performance
- November 1958
Education, July 1963
- Treachery of Judas,
- The Sucker, May 1963
Stereotaped New Year, January 1963
- The Snow Machine, December 1960
Extracurricular Education, July
- Slow Motion for Quick Action,
- Sonar Sleuthing, August
- TV Antennas, August 1955
Succoring a Soroban, March 1963
"All's Fair --", September 1963
Operation Worm Warming, May 1961
- The Crazy Clock Caper, October 1960
- Two Detectors, February 1955
Tussle with a Tachometer, July 1960
- Therry and the Pirates, April 1961
The Sparkling Light, May 1962
Pure Research Rewarded, June 1962
Hot Idea, March 1960
- The Hot Dog
Case, December 1954
- A New Company
is Launched, October 1956
the Mistletoe, December 1958
Eraser, August 1962
- Blubber Banisher,
- "BBI", May 1959
Ultrasonic Sound Waves, July 1955
- The River Sniffer, July 1962
Ham Radio, April 1955
El Torero Electronico, April 1960
Wired Wireless, January 1962
Electronic Shadow, September 1957
- Elementary Induction, June 1963
- He Went That-a-Way, March1959
Electronic Detective, February 1958
- Aiding an Instinct, December 1962
Posted September 17, 2014