Category Archives: Telephone history

Emergency Telephone Hookup

PhoneIntercom

It’s a relatively trivial matter to hook up two telephones so that you can talk from one to another. Virtually any old telephone can be used, and it’s simply a matter of placing a battery (the voltage is not critical) in series. So if you need to hook up two telephones to talk, it’s about as easy as it gets.

It’s more difficult, however, to figure out a way to make the other telephone ring. The telephone itself operates off DC. The ringer sounds when an AC voltage is applied. And there’s no particularly simple way of generating that AC voltage. The easiest way to solve the problem is to run a second circuit with a bell, buzzer, or light. If you want to talk to the other station, you push a button, a bell (separate from the phone) sounds at the other end, and the other person picks up the phone.

The ingenious arrangement shown above shows a way to wire it all up so that a single circuit can handle both the bell and the telephone line. When one station wants to call, he pushes the button to signal the other station. Then, both sides put the switch on position 2, and they can talk. This circuit, and all the details for constructing it, are found in the April 1966 issue of Radio Constructor, a British electronics magazine.

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US-Japan Radiotelephone Circuit, 1935

JapanOperatorSix years before the attack on Pearl Harbor, radiotelephone service was inaugurated between the United States and Japan. Shown here is Chiduko Kashiwagi, the Japanese telephone operator at the Tokyo end of the circuit. The radio link was between the transmitting stations at Dixon, California, and the receiving station at Komuro, Japan. The signals going the other way went from Nazaki, Japan, to Pt. Reyes, California. The control points were located at San Francisco and Tokyo, from which points the signals were linked to the respective national telephone networks.

JapanRXTo ensure secrecy, the signals were scrambled. The Komuro receiving station is depicted here. The U.S. transmitting station at Pt. Reyes had a signal of about 20,000 watts.

References

 

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Merry Christmas!

Santa1914Santa hasn’t changed a great deal over the last hundred years.  Here, he’s shown in a 1914 Ohio newspaper, answering the phone.

The accompanying advertisement reminds readers how much more convenient both Cristmas and life in general would be if they had a telephone installed in their homes.

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German Field Telephone, 1914

GermanFieldTelephone

A hundred years ago today, the Philadelphia Evening Ledger, November 30, 1914, carried this photo of a German field telephone in use.  The caption notes that the Germans’ extensive telephone network has made much trouble for the Allies.


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Army Signal Corps Field Buzzer, 1916

U.S. Army Signal Corps Field Buzzer. Technical Equipment of the Signal Corps: 1916.

U.S. Army Signal Corps Field Buzzer. Technical Equipment of the Signal Corps: 1916.

A hundred years ago today (September 21, 1914), the Calumet (Mich.) News carried an article entitled, “Communication Big Factor in Modern War Machinery,” which explained the technological developments in communications in use in modern warfare. The article runs down the developments in telegraph, telephone, and wireless in use in the war.

One that caught my attention was a rather ingenious telephone-telegraph that was used in situations where the lines were in poor shape. As the article points out, lines near the battlefield “are often laid at high speed, are of high resistance and are frequently leaky.” In those cases, it described a “special instrument known as the buzzer.”

It describes the instrument as a metal-lined leather case with a dry battery, induction coil and interrupter, key, telephone transmitter, and telephone receiver. It could be used as a field telephone, or by use of the buzzer, the key could send out an intermittent current which would traverse the line where the distant receiver would give out a sharp note. Thus, the telephone could be used to send Morse code via audio.

It notes that these “Morse signals are audible over an incredibly bad line.” It cites one case where a signal was successfully sent over bare wires lying on wet ground.

The schematic of the instrument is shown here:

The field buzzer itself is shown above as it would be carried, and it is shown dismantled here:

This diagram of a typical hookup of the buzzer shows its use with a line of dubious quality:

 

References

Camp Telephone for the Army, Telegraph and Telephone Age, July 1, 1917, page 302.


 

Completion of the Transcontinental Telephone, 1914

TranscontinentalTelephoneA hundred years ago, it became possible for the first time to make a telephone call from coast to coast. The September 1914 issue of Popular Mechanics reports that the line from Denver to San Francisco had been completed on June 17, 1914. On that date, crews working westward from Salt Lake City and eastward from San Francisco met at the Nevada-Utah state line. The lines were spliced together at a pole erected on the state line and “the last splice was accompanied by a ceremony much like that of driving the last spike on a transcontinental railway.”

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