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Mac's Radio Service Shop: Telephone Pickups and Other Subjects
April 1954 Radio & Television News Article

April 1954 Radio & TV News
April 1954 Radio & Television News Cover - RF Cafe[Table of Contents]

Wax nostalgic about and learn from the history of early electronics. See articles from Radio & Television News, published 1919-1959. All copyrights hereby acknowledged.

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Tele-Tape Productions camera (EyesOfAGeneration.com)

At least in the U.S., laws regarding the recording of telephone conversations seem to be constantly changing and vary from state to state. Violation penalties - including imprisonment - can be severe in both cases. Some states require that all parties in the conversation be apprised of the recording, while others only require that at least one party (obviously the one doing the recording) be aware of it. As mentioned in this 1954 Macs Radio Service Shop story, some areas require that an audible "beep" be sounded at regular intervals while recording is occurring. With the ubiquitous use of smartphones featuring built-in recording capabilities, opportunities for recording and being recorded are constant. Cave participantium, to coin a phrase. As with carrying concealed weapons or just transporting them between states, if you have any intention of recording a telephone conversation, you had best check on the most recent statutes before-hand.

Mac's Radio Service Shop: Telephone Pickups and Other Subjects

Mac's Radio Service Shop: Telephone Pickups and Other Subjects, April 1954 Radio & Televsion News - RF CafeBy John T. Frye

The calendar said April, but the drifting snowflakes outside the service shop window looked more like the middle of January. Barney turned away from the depressing sight and went back to join his boss at the service bench.

"One of the few advantages of growing older," Mac murmured, "is that you learn to take the weather as it comes instead of fretting about it."

"Don't talk to me about weather," Barney growled. "Talk about anything else. Even give me one of your long-winded technical lectures."

"Ignoring that 'long-winded' adjective," Mac said with a grin, "I might chatter away a bit. The other day you asked me whether or not it was legal to use inductive-type pickups for recording telephone conversations. You argued, as I remember, that since no direct connection was made to the telephone wires, 'it was nobody's business,' as you put it, if you wanted to use one of these gadgets."

"So?" Barney questioned.

"So I wrote to the FCC for an opinion. They sent me back copies of pertinent reports and orders, together with a letter. It all boils down to about this: (1) You cannot use a recording device in connection with interstate and foreign message toll telephone service without all parties to the telephone conversation being notified that telephone recording devices are being used. (2) Only one form of such notification is acceptable. (3) This is the notification produced by a recurring signal of certain specified characteristics. (4) The specifications for this signal, produced by an automatic warning device, are as follows: The signal consists of a single tone having a pitch of 1400 cycles per second, plus or minus 10%. This tone is injected into the telephone line in the form of 'beeps' having a length of 20/100 of a second, plus or minus 20%. These beeps must occur at intervals not less than 12 seconds nor more than 18 seconds apart. The signal strength level of the beeps must equal the average telephone talking level."

"You mean I can't just say to the guy on the other end, 'Joe, I'm recording this,' and let it go at that?"

"That's right. Only the automatic tone signal can do the notifying that a recording is being made. When the recorder is directly connected to the line, the telephone company furnishes an automatic signaling device that produces the beep signal whenever the recorder is working; but when you use an inductive type of pickup, the problem is different. The FCC says that as far as it knows, no automatic tone warning has yet been developed to operate with a recorder employing an induction-type pickup.

"Of course the FCC's order only applies to interstate and foreign telephone conversations. It does not apply to local and intrastate calls. However, the FCC says it understands similar tariff regulations have been filed by local and intrastate telephone companies with their regulatory agencies. I know our telephone book has a statement that the recording of a telephone conversation without introducing the 'beep' signal is unlawful. I notice on the box in which one of these induction pickups is packed that there is a warning that it cannot be used for recording interstate calls without the beep. It goes on to say that the FCC ruling does not apply to intrastate calls and that some states require a warning tone while others do not."

"It looks like the thing for me to do is to get busy on inventing a gadget for producing the beep signal without having to make a connection to the line," Barney commented. "Really, though, I'm not sure I'll have time. Since I read where color television had been recorded on tape, I'm concentrating on my TeleTape Camera."

"How will that work? if I may be so foolish as to ask," Mac quizzed.

"Without giving away too many secrets, I can tell you it is a sort of movie camera, complete with sound, that uses magnetic tape for film. I simply load up the camera with a roll of tape and go out and shoot a few shots of bathing beauties gamboling on the beach. Their merry shrieks of girlish laughter are recorded on one track of the tape. The rest of the tape is used to record the light images that have been transformed to magnetic pulses in the various transistorized circuits of my camera. Then I take the tape home and put it on a playback device plugged into the TV set. Right away the girls, in full color, mind you, start gamboling on the screen of the TV receiver, and the before-mentioned girlish laughter comes from the speaker. If I should ever grow tired of this entertainment - may that never happen! - I can simply erase the tape and put it back into the camera for taking other pictures."

"How far are you along with this invention?" Mac asked.

"Well, I bought a transistor yesterday," Barney replied.

"That's about what I thought," Mac remarked dryly; "but the basic idea may not be as wacky as you suppose. Really, almost all of the know-how for such a camera has been uncovered. Now, though, suppose we quit day-dreaming and do a little work, just for kicks. What is the matter with that little set? You've been on it since yesterday."

"If I knew what was wrong, I'd fix it," Barney replied tartly. "The little cuss has a strong a.c. hum that appears only when a station is tuned in. At first I thought that would be a snap. Usually this happens when the condenser across the line opens up; but in this case, that condenser was all right. I tried a new one to be sure. Then I decided that possibly the tuning condenser frame was shorting to the chassis. No dice there, either. Next I substituted new filter condensers for I have seen cases where a fault there will produce that condition although usually a poor filter condenser results in a hum that is present all the time instead of just being present when a station is being received. That was no good either. I did not expect it to help because it looks as though new filters had been put in not long ago. Right now I'm fresh out of ideas. You got any?"

Mac turned the little chassis up-side down and did some wire tracing in the vicinity of the filter condenser connections. Then he cut a lead loose from one tie-point and resoldered it to another. Next he turned the receiver on and tuned it across the band. No hum was heard on any station.

"Oh quit looking like you had just found The Lost Chord," Barney said disgustedly. "Go on and tell me how dumb I was."

"No, I do not think you were dumb," Mac said gently. "As usual, though, you were too busy looking for the trouble to stop and think about it. This kind of hum is always produced by something that modulates the r.f. or i.f. signal at the hum frequency. That is what you should have been looking for. The clue to the cause of the trouble was the fact that the filter condensers had recently been replaced. You will note that a can-type, twist-prong condenser was replaced with a cartridge type. That meant all the leads going to the prongs of the original condenser had to be removed and transferred to the wire leads of the new unit. The technician who did this got a little confused and transferred the plate lead for the i.f. stage from the output of the filter to the input. This placed considerable ripple voltage on the plate and screen of that tube. Since it handled only i.f. frequencies, this ripple produced no hum as long as no carrier signal was being passed by the i.f. stage.

"When a carrier was being received, however, this carrier was modulated by the ripple voltage. When this hum-modulated carrier was detected, the hum voltage appeared in the output. I simply put the plate and screen lead back to the output of the filter, where it belongs, and that cleared up the trouble."

"It sounds so easy when you explain it," Barney said with a sigh.

"If it will make you feel any better, I'll tell you about a case I did not solve so easily," Mac said consolingly. "Last week I went out on a call in which the complaint was that the sound was causing interference in the picture. Naturally, I decided one of the sound traps was out of adjustment, but no amount of adjusting in the cabinet would cure the condition. Next I decided that possibly something was wrong with one of the traps; so I pulled the chassis and brought it to the shop. It was one of those chrome-plated custom chassis of the 630 type with separate sound and picture. The fellow had bought a cabinet and had done a fine job of installing the chassis and a hi-fi speaker.

"When I put the chassis on the bench and turned it on, the trouble was gone! Not the least trace of sound interference could be seen in the picture. Apparently the ride to the shop had cured whatever was wrong. Naturally I tapped and pounded the set all over in the hope that I could make the trouble show up again, for, like all technicians, I despise a set that seems to cure itself; but nothing I could do would make the trouble come back. The only thing to do was return the chassis, which I did. I put it back into the cabinet and turned it on, and the same old trouble was right there!

"With a very red face I pulled the chassis again, but this time I set it on the floor beside the set and turned it on. The sound bars were gone. It began to dawn upon me that there was something inside the cabinet that caused the trouble. A careful examination revealed that the owner had installed two two-inch-wide tin strips on either side for the feet of the chassis to ride on when he slid the receiver in and out of the cabinet. These rubber-mounted feet had little projections on the bottom that bit into the wood and made the heavy chassis extremely hard to slide until the tin strips were installed. The picture and sound i.f. channels were mounted side by side on the same side of the chassis. One of the strips ran directly beneath the i.f. transformers of both channels. I decided that possibly this tin strip, which was insulated from the chassis, was coupling the sound i.f. back into the picture i.f. The sound traps were up near the tuner, but the coupling might be taking place from the output of the sound i.f. - where the signal strength would be greatest - right over to the picture i.f. at a point where no more sound traps appeared between there and the detector.

"To test the theory, I put the chassis back into the cabinet and shorted the tin strip to the chassis with a screwdriver. Instantly the sound interference almost entirely disappeared. It was only present on one channel. A little figuring revealed that the strip was a quarter wavelength long on that channel. Removing the tin strip cured the trouble completely. Now do you feel better to see how easily I was stumped?"

"I dunno," Barney muttered. "When you have troubles, you solve them; but when I have problems, you have to solve them, too."

 

 

Posted May 20, 2020


Mac's Radio Service Shop Episodes on RF Cafe

This series of instructive stories was the brainchild of none other than John T. Frye, creator of the Carl and Jerry series that ran in Popular Electronics for many years. Mac's Radio Service Shop began life in Radio & Television News magazine (which itself started as simply Radio News), and then changed its name to Mac's Service Shop after the magazine became Electronics World. 'Mac' is electronics repair shop owner Mac McGregor, and Barney is his eager, if not somewhat naive, technician assistant. 'Lessons' are taught in story format with dialogs between Mac and Barney.

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