Professor Clarence Freeman of the Armour Institute became interested in de Forest's work and developed a new type of spark transmitter.
12.
Even when vacuum tube based transmitters had been installed, many vessels retained their crude but reliable spark transmitters as an emergency backup.
13.
Damped wave spark transmitters were replaced by continuous wave vacuum tube transmitters around 1920, and damped wave transmissions were finally outlawed in 1934.
14.
Use of the spark-gap transmitter led to many radio operators being nicknamed " Sparks " long after they ceased using spark transmitters.
15.
Most high power gas-discharge street lamps ( mercury and sodium vapor ) still use modified spark transmitters as switch-on ignitors.
16.
Beginning in 1905, demonstration radiotelegraph stations, using spark transmitters and electrolytic detectors, were installed for evaluation by the U . S . Navy.
17.
While the various early systems of spark transmitters worked well enough to prove the concept of wireless telegraphy, the primitive spark gap assemblies used had some severe shortcomings.
18.
Most operators, however, still preferred spark transmitters because of their uncomplicated design and because the modulate the carrier and to prevent transmitter leakage from de-sensitizing the receiver.
19.
As late as 1955, a Japanese radio-controlled toy bus used a spark transmitter and coherer receiver; the spark was visible behind a sheet of blue transparent plastic.
20.
Some early CW transmitters employed an arc converter that could not be conveniently Spark transmitters used for this method consumed a lot of bandwidth and caused interference, so it was discouraged by 1921.
