One of two telephones used by Alexander Graham Bell in a demonstration that took place between Boston and Salem, Massachusetts on November 26, 1876. Critical features are the iron diaphragm (seen as a black circular disc mounted on the vertical wooden support), two electromagnets (seen in white, facing the diaphragm) and a horseshoe permanent magnet (lying horizontal, pressed against the electromagnets).
When used as a transmitter, sound waves at the mouthpiece cause the diaphragm to move, inducing a fluctuating current in the electromagnets. This current is conducted over wires to a similar instrument, acting as a receiver. There, the fluctuating current in the electromagnets causes the diaphragm to move, producing air vibrations that can be heard by the ear. This was a marginal arrangement, but it worked well enough to be employed in the first commercial services in 1877. The magneto receiver continued to be used, but the transmitters were soon replaced by a carbon variable-resistance device designed by Francis Blake and based on a principle patented by Thomas Edison.
Mahogany base mounting a glass tube containing iron filings -- a brass cased striker, a sounder, and relay. Marked "L.E. Knott Apparatus Co., 16 Ashburton Place, Boston, Mass." When a radio signal passes through the tube, the metal filings "cohere" or link together, closing an electrical circuit. Tapping the tube causes the filings to disassociate, opening the circuit. This was one of the earliest forms of radio signal detectors.
Telegraph relays amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, to the point where the incoming signal was too weak to directly operate a receiving sounder or register. A relay detected a weak signal and used a battery to strengthen the signal so that the receiver would operate.
This relay was made by John Polsey & Company of Boston, a firm better known for making clocks. Polsey (1816-1873) established the firm about 1859 and closed it in 1864. Western Union Company donated the relay to the Smithsonian in 1904 and reported that the relay was "a relic of the Confederacy and was used at Fort Sumter by W. R. Cathcart, manager for many years of their Columbia, SC office who was stationed at that fort as a military operator."
Marked: Tower Mfg. Corp. / Scientific / Navy Type / Boston, Mass. / U.S.A." Standard head telephones with pin plugs at end of cloth-insulated cord. One plug is broken off. D.C. resistance unmarked but presumably 2000 ohms. Double headband. Original price: $2.95. Reference: Radio Broadcasting, February 1925, page 848.
Marked: Unit: "Holtzer-Cabot / Boston / Universal / Made in U.S.A. / Connect terminal with +mark to the terminal on the amplifier which goes to the +side of the "C" battery." Box: "Tower Scientific loud speaker phonograph attachment for Victor, Columbia, Pathe, Vocalion, Standard, Sonora, Silvertone, Edison and Jewel Tone Arm. " Binding posts on the base. This may not be the original box.
This unit is an electroacoustical coupler, designed to connect the audio output stage of a radio receiver to a standard acoustical phonograph. They were advertised as cures for the 'unsightly' loudspeaker which generally had a horn shape at the time. Basically a magnetic headphone, coupling was achieved by inserting the pickup needle into a reed on the driver.
Marked: Radiola IX / Radio Phonograph adjunct / Radio Corporation of America / Receiver and Radio Audio Amplifier / Model AR1396. Patented: 1/15/07; 1/21/08; 2/18/08; 4/12/10; 7/6/12; 10/6/14; 1/23/17; 3/13/17; 7/3/17; 10/22/18; 1/7/19; 12/23/19; 6/15/20; 7/6/20; 4/19/21; 12/274/21; 8/22/22. Made by wireless Specialty Apparatus Co., Boston USA. Inspection tag reads Job No. 9121-7, Serial No. 3152. Assembled by Surette Staick / Date: 5/26/24. Radio receiver consisting of all pertinent components mounted on 17.5" square panel. Chassis only, to be mounted in place of the lid in a console phonograph as an accessory / upgrade. UV201A tubes are normally employed (missing from unit). Circuit appears to be TRF type using two RF stages, detector, and two stages of audio. Controls on the front panel include antenna and secondary tuning, volume control, filament rheostat and selector switch. Secondary inductance coils consist of three spider web coils mounted in a fixed coupling arrangement. Battery cable and antenna are provided. Reference: Radio Manufacturers of the 1920's, Vol. 3.
