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About RF Cafe
1996 - 2016
BSEE - KB3UON
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 Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...
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July 1936 Radio-Craft[Table of Contents]
People old and young enjoy waxing nostalgic about and learning some of the history of early electronics. Radio-Craft was published from 1929 through 1953. All copyrights are hereby acknowledged. See all articles from Radio-Craft.
It really was not all that long ago when wiring images for news stories literally meant transmitting photographs over a twisted pair of telephone lines either to a fax machine or to a computer on standby waiting for incoming files. Videocasts were being regularly performed via satellite of ground relay microwave stations since the 1960s, but most still shots were sent via phone lines. For the last decade and a half, both still shots and videos have been transmitted as a routine matter via camera-equipped cellphones, and as with most technologies we have quickly become so accustomed to the convenience that memories of the old ways are quickly (even thankfully) forgotten. This article from a 1936 edition of Radio-Craft describes one of the really early systems. Notice that coupling to the telephone line is via induction to the handset, not via a hardwire connection to the phone circuit. The thumbnail on the left links to a 1940 news story in the Monroe, Louisiana News-Star newspaper boasting of its newly acquired telephone photo system.
A newly-perfected system for sending news photos over ordinary telephone lines is here described. The portable transmitter is not connected directly to the line but is merely placed close to the telephone instrument. A "picture" may be telephoned at night from coast to coast for only $25!
One of the most important aids to the modern high-speed dissemination of pictures of news events has come to light recently with the release by the New York Times of data on a system of wire transmission of photos, developed by its subsidiary, Wide World Wired Photos. This new method employs the wires of the telephone companies, and in some cases those of the telegraph carriers as well, without actual connection to the circuit. The impulses from the portable transmitter are transferred to the lines by induction only, and will function anywhere there is an ordinary telephone line, which is the feature that makes its field so enormous.
The transmitters, as seen in Fig. A, are of the portable type, and weigh about 50 lbs., packed in their carrying cases, which are not much larger than a good-size suitcase. If operation is to be accomplished at a point where line power is not available, the equipment may be operated from any 6 V. source, such as a storage battery. A 15-lb., airplane-type battery will supply sufficient current to transmit 8 full-size (7 1/4 x 8 3/4 in.) images or "pictures."
The receivers, as seen in Fig. C, are of the rack type since they need not be portable, and may be operated in either light or dark locations.
Actual operation of both transmitters and receivers is very simple. An ordinary glossy photo is secured to the drum of the transmitter, which in operation revolves 45 times per minute. As it turns, a spot of light photo to a photo-cell, the resulting current being combined with an 1,800-cycle signal. This combination signal is then amplified and applied inductively to the line. (It is only necessary to cover the transmitter of the telephone instrument, so as to prevent pick-up of external noise.) An ordinary station-to-station call is then made over the telephone to the newspaper office; (later, use may be made of the "conference wires" whereby the pictures may be sent from one point and received simultaneously at several different cities).
At night rates, a 6 1/2 x 8 1/2 ins. picture would cost a maximum of about $25.00 if sent from coast to coast, and could be sent in about 15 mins.
The receiving end operates almost as simply. The operator places a drum carrying a sheet of sensitized paper upon a vertical spindle on the panel. A pick-up coil placed close to the telephone instrument is connected to the amplifying system of the receiver, and the amplifiers and synchronizer adjusted, the latter process being extremely simple.
While the process is somewhat similar to that used by other news systems, it differs in several important points, one of the most radical departures of course, being that the portable transmitters may be used anywhere there is an ordinary telephone line available. Another difference is that the new apparatus is so well synchronized that perfect pictures may be sent over the "carrier circuits," used quite extensively in the Southwestern portion of the U. S. Transmission over these circuits heretofore has resulted in such distortion that the pictures were totally unusable.
The perfection of the transmissions may be seen by reference to Fig. B, which shows an unretouched photo of a railroad wreck as reproduced over the system; and Fig. D, also unretouched illustrating an actual "news" occurrence.
In Fig. 1, our artist has shown the sequence of operation. First the reporter snaps a picture of a wreck, which is then quickly developed, and transmitted over the telephone in the village general store. The reader will easily understand the importance of this rapid system in the dissemination of illustrated news stories.
Posted March 29, 2016