Stamped on top: "L. E. Knott Apparatus / - Co. - / Boston" - clear glass jar 2/3 covered with lead inside and outside, wood top with ball-tipped rod and brass single-jack chain. Appears to be a model 85-15, quart sized jar as seen in the Knott 1912 catalog, page 398. Original price: $1.60.
A rotary wall switch with a ceramic base, nickel-plated cover and plastic knob. "Und. Labs Inc. G. E. Co. U.S.A. 3A 250V 5A 125V" on cover, "GE 239" written on back, "N.P. 1133 [LA?]" on indicator plate. GE logo on knob.
Telegraph keys are electrical on-off switches used to send messages in Morse code. The Mecograph Company created a right-angle semi-automatic telegraph key around 1906. They competed with Horace Martin's Vibroplex Company until Martin purchased Mecograph in 1914. A semi-automatic key repeated the Morse code dots rapidly, much like holding down a key on a keyboard for repeated letters. The operator still keyed the dashes but could work much faster.
Telegraph relays amplify an electrical signal in a telegraph line. Telegraph messages travel as a series of electrical pulses through a wire from a transmitter to a receiver. The pulses fade in strength as they travel through the wire, limiting the distance a message can be sent. Relays remedy that problem by detecting a weak signal and automatically re-transmitting that signal down the line using a local power source.
Leyden jars were essential for storing electrical charges used by the earliest wireless radios used aboard ocean liners. Shortly after RMS Carpathia's rescue of Titanic survivors, the ship visited Boston, Massachusetts. Marconi Wireless Radio employee Harry Cheetham boarded Carpathia to service the radio, which had been damaged during the Titanic operations. He replaced these two Leyden jars. One is intact and the other is broken, but fortunately the broken one shows how the jars were constructed inside to store and relay an electrical charge. Cheetham kept these artifacts as Titanic souvenirs, and donated them to the Smithsonian in 1930.
A variable resistance consisting of a copper coil wound on a ceramic mandrel, mounted on a wooden base. A sliding contact mounted above the coil is used to vary the electrical resistance of the unit. Two binding posts allow connection to external circuit. Donor was Robert Williams Wood (1868-1955), professor of optics at Johns Hopkins University (1901-1955).Unit may have been used to control the light output of a flash telescope military signaling device during World War I.