Radio Related Links
ARRL Website
Atwater Kent Website


The Crosley Radio Gallery

You are in


Today, most television and radio information is sent in Digital format. Sending of digital signals in the broadcast industry began with the satellite era. Modern TV and radio stations only switched to broadcasting in digital format a few years ago. If someone were to ask you when the use of "digital" communications began, what year would you guess? Perhaps the year Sputnik was launched into orbit, or would it have been the year when the first world-wide television transmission was made?

If your guess falls along these lines, then you are totally wrong! Digital communications began with the use of the telegraph in the mid 1800s. You see, Samuel Morse's "on-off" electrical impulses that form the dots and dashes of his alphabetical code, are in fact the world's first truly "digital" transmissions of intelligent information. Digital information is made up of '1s' and '0s'. A one indicates data is present, and zero indicates a pause between that data. The number of 1s and 0s in a string, equates to the facsimile data that forms our television and radio and computer program information. Morse Code uses that same principle, although on a simple scale, to do exactly the same thing, so in fact Samuel Morse discovered digital communications long before any of us were even alive.

Samuel Finley Breese Morse (April 27, 1791-April 2, 1872) is credited with the practical introduction of the telegraph in America. Morse, however, was primarily trained as an artist, and he later a became recognized as a controversial religious and political figure who believed in staunch Federalism. Although his single-wire telegraph system became the standard in America, it was patterend after a system that had already been developed in Europe.
Advertising sign for Western Union local telegraph offices.
A sampling of items from the museum's Samuel F.B. Morse telegraph Collection.
The museum's display case of antique telegraph code keys, sounders and relays.
A 1931 Western Union-IC Railroad cooperative identification card for a Western Union Telegraph Company agent.
Code cipher book from the Baltimore & Ohio Railroad
A collection of early telegraph keys and sounders used by Western Union and the Railroads
A brass telegraph key dating to the late 1800s. Keys such as this were used in railroad service, and were still in use during World War I.
1850s hand made Galvanometer used for checking telegraph signals.
An extremely rare artifact from the late 1800s is this mechanical telegraph tape "ticker." These devices were used to record telegraph messages on to paper tape for archival purposes, or for later reading when the telegrapher was unavailable to directly receive an incoming message. They were found in railroad and telegraph offices, and were also used by police and fire alarm dispatchers as a way to archive the activation of emergency call boxes and central alarm systems.
This magazine which dates from May of 1893, was the official journal of railroad telegraph operators.

From the early 1930s through World War II and beyond, the Instructograph was widely used to train telegraph operators in both the military and private sectors. These machines used punched paper tape to control a tone generator which produced code characters for students to practice translating.

Click the image above to see a complete manufacturer's manual on the Instructograph.

This extremely rare item above is a World War I field telegraph transceiver built for the U.S. Army Signal Corps. It was a complete telegraph send and receive unit that could be attached to permanent or temporary telegraph lines by soldiers in the field.
By the year 1929, The Boy Scouts Of America organization had become aware of the opportunities that knowledge of Morse Code could make in conjunction with camping and general readiness of scouts to step into emergency service roles. An official Scout merit program for code proficiency was started, and the device shown above became the officially recognized Boy Scouts code device for both practice and actual message transmission.
In the early days of telegraph and telephone, separate circuits were required in order to process messages and calls to multiple destinations. In many cities, spider webs of wiring, as shown above, took over the skyline. Later, scientists and engineers discovered that multiple signals could be carried on a single cable, known as multiplexing. This technology drastically reduced the amount of wire used on the communications systems. Today, with fiber optic and laser technology, tens of thousands of simultaneous calls and messages can be processed by a single circuit through the use of multiplexing techniques.
A railroad station telegrapher at work
Telegraph Sounder in amplifying box, typical of those used in railroad station offices around the turn of the century. It was not unusual to find a pocket-sized metallic Prince Edward tobacco tin laid in these instruments. That particular container was discovered to further enhance the volume of the "clicks" produced by the sounder.
More telegraph keys and sounders from the railroad telegraph era
Top arm of a railroad telegraph pole with glass insulators
A collection of telegraph insulators used by the various railroads and telegraph companies.

1920's selective telegraph annunciator used by American District Telegraph Company

By the early 20th Century, telegraph had become sophisticated to the point that many routine functions had been automated. The invention of the Telephone, followed by the wide availability of telephone service in most areas, sealed the eventual fate of wired telegraph service, however, telegraph technology continued to be employed in the security industry, as a method of remotely monitoring homes and buildings for the occurrence of fire or burglary. Telegraph companies, such as Western Union, also continued to send and receive messages, through the use of wired telegraphy, well into the 20th Century.


The early 1900s photo above illustrates a typical spark type radio transmitting plant on an ocean going vessel.

In the years surrounding the turn of the 19th / 20th Centuries, it had been discovered that the electrical impulses from an open electrical spark, would carry through the air. Scientists realized that this would somehow make it possible to send telegraph signals between two physical locations without the use of wires.

Commercial interests such as the Marconi Company, and amateur experimenters as well, began to employ and expand this new technological discovery, and before long, wireless telegraph transmitting stations started coming into existence. Early stations did not have the luxury of the use of the yet to be perfected Vacuum Tube, so the technology involved mostly high voltage producing transformers and generators, along with inductive tuning circuits to attempt to limit the frequency range of the spark produced signal. This gave rise to such devices as the rotary spark gap, a motor driven wheel on which numerous spark gaps were placed around the circumference of a wheel. Reception, which required rectification of the spark produced radio frequencies, was limited first to coherer type detecting devices, and later to detectors made of galena crystal.

By the early 1920s, and with the perfection of the Deforest Audion, vacuum tubes had come on the scene. Spark generation of radio signals was soon replaced by vacuum tube generated radio frequency signals, which could be tuned much more specifically to a particular frequency and bandwidth. Tubes also made it possible to amplify and rectify signals, with tuned accuracy, which eliminated the need for the earlier crystal type detectors. Wireless telegraph, however, remained in use in commercial shipping and long distance communications for most of the 20th Century. The ability of Carrier Wave code type signaling to penetrate long distances via radio, made it an ideal way to communicate with ships at sea, and stations separated by many miles, oceans and continents. It was not until the wide-spread use of cellular telephone and satellite based communications, that the need for wireless transmission of carrier wave signals came to a practical end.

Shown below are some relics of the "Spark Era" of radio's history, that are housed in the museum collection.

A typical Rotary Spark Gap used in early "spark era" CW transmitter

Above, an authentic 1905 Spark transmitter using a Tesla type induction transformer. This transmitter was an experimental amateur radio project that came from the estate of an early amateur radio operator.

Below: A replica of a 1/2 Kilowatt Marconi era transmitter that is used as a demonstration piece for tours at the museum. It is constructed with original components, and is symbolic of the type of high-energy spark transmitters used in the ship-to-shore CW stations toward the end of the "Spark" radio era.

For many "spark era" amateur radio operators and experimenters, automobile ignition coils, such as this example taken from an early Model T Ford, provided easily obtainable sources of high voltage that were required to produce spark generated radio signals.
An early example of a spark transmitter built for use in an amateur radio station.

The museum's extremely rare Alexander Graham Bell design telephone voice transmitter

With the discovery of Lee Deforest's vacuum tube, Marconi's experiments in radio wave propagation, and Alexander Graham Bell's discovery of the microphone, the device that could turn sound waves into electrical signals, the field was ripe for the development of commercial voice and music radio broadcasting. In the following galleries, you will see how the inventions of several scientists and inventors all came together to give us the ability to broadcast voice and music over the air waves.

As we approached the year 1920, radio experimenters were just beginning to understand how to use the newly introduced Deforest Audion as a replacement for primitive high voltage spark technology. This early experimental voice modulated RF oscillator is an example of how technology from the telegraph, telephone and radio fields of scientific research were coming together to give us sound modulated radio transmissions.

Ok, now that I have shown you the transmitting station components of early wireless radio-telegraphy, we move on to the next gallery where you will see the story of the creation of the telephone. We will visit that gallery first before we move on to the gallery of early radio receivers because it is important to understand some basic telephone technology since it played a large role in the development of early radio broadcasting.

Alexander Graham Bell's invention of wired voice transmitting technology was important at this step in the development of radio also. Many of Bell's audio processing principles carried over into the Radio sector, including the microphone, the earphone (which eventually evolved into the loud speaker,) and also the eventual nation-wide wired network that, along with telephone communications, also made possible the radio networks such as NBC, CBS and others.

Remember that Dr. Lee DeForest's vacuum tube had not yet become a staple of radio design, so in the early radio gallery you will first see some early radio receiving sets which did not make use of vacuum tubes. The first receiving mechanisms around were mechanical "coherers" which used common materials like iron powder to provide a visual image of the transmitted character. Right on the heels of the coherer, scientists discovered that the Galena crystal, a glass-like rock found in nature, could function as a "detector" to receive signals sent by the early spark transmitters. Please follow me on our adventure by clicking the "to next gallery" button below.

Copyright 2014, The Museum Of Yesterday, Chesterfield, VA USA