A small, vertically mounted motor. Two-piece frame with 5/8" wide electromagnet coil at bottom and a 3-section armature mounted above. Pulley on one end of armature and commutator with make-shift wire and leaf-spring brushes on the other. Open frame construction, plate on top has been removed. No extant maker's marks.
A 2-prong current tap with two polarized connector positions. Plastic shell with brass tines, one horizontal, one vertical. Molded on top: "10A 250V / 15A 125V".
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.
Marked: "Portafone / R1926". In the U.S. Patent Office, Lowell and Dunmore Exhibit No. 57. Believed to be the second Portaphone receiver. Unit is a six-tube tuned radio frequency receiver employing 215A "peanut" tubes. Case is actually a leather suitcase with a diaphragm-driven speaker horn and a coil antenna mounted in the top lid. Two 1.5 volt dry cells are strapped into the bottom of the case to provide filament voltages. An external plate battery was apparently used. The loudspeaker horn opens through an aperture in the cover of the leather case. This portable self-contained receiver was constructed by P.D. Lowell & F.W. Dunmore before the middle of 1921, and was demonstrated to visitors at the Bureau of Standards Radio Laboratory by Richard S. Ould, an electrical engineer who testified as a witness in the patent office Interference proceedings. An earlier model of the "portafone" was demonstrated before Alexander Graham Bell in May of 1921, and received radiotelephone broadcasts form station NSF in Anacostia. Reference: In the U.S. Patent Office" "Record and Testimony on Behalf of Lowell and Dunmore" (1928), page 503.
Marked: "Amperes / General Radio Co. / Model 127B / No. 8563". An antenna current meter with O-2 Amp. scale. Reference: General Radio Catalogue C, "Radio Laboratory Apparatus" (1920), page 63.
Jenkins prismatic lens disc scanner. Ground glass prismatic disc, 10" diameter, hand actuated by a mechanical linkage. Empty metal cylinder opposite linkage. Marked Jenkins #6. Originally recorded (1921) as "a model high speed motion picture camera for the analysis of motion. Construction: disk ring prism for hinging the light beam to produce motion pictures from continuous motion picture film with only rotary mechanisms." A later note (1932) recorded this as a "lens-disc receiver for projecting television pictures onto a screen."
Irving Langmuir received a Ph.D. in physical chemistry in 1906 from the University of Göttingen. He studied under Walther Nernst, who had invented a new type of incandescent lamp only a few years before. In 1909 Langmuir accepted a position at the General Electric Research Laboratory in Schenectady, New York. Ironically, he soon invented a lamp that made Nernst's lamp (and others) obsolete.
Langmuir experimented with the bendable tungsten wire developed by his colleague William Coolidge. He wanted to find a way to keep tungsten lamps from "blackening" or growing dim as the inside of the bulb became coated with tungsten evaporated from the filament. Though he did not solve this problem, he did create a coiled-tungsten filament mounted in a gas-filled lamp—a design still used today.
Up to that time all the air and other gasses were removed from lamps so the filaments could operate in a vacuum. Langmuir found that by putting nitrogen into a lamp, he could slow the evaporation of tungsten from the filament. He then found that thin filaments radiated heat faster than thick filaments, but the same thin filament–wound into a coil–radiated heat as if it were a solid rod the diameter of the coil. By 1913 Langmuir had gas–filled lamps that gave 12 to 20 lumens per watt (lpw), while Coolidge's vacuum lamps gave about 10 lpw.
During the 1910s GE began phasing-in Langmuir's third generation tungsten lamps, calling them "Mazda C" lamps. Although today's lamps are different in detail (for example, argon is used rather than nitrogen), the basic concept is still the same. The lamp seen here was sent to the National Bureau of Standards in the mid 1920s for use as a standard lamp.
Lamp characteristics: Brass medium-screw base with skirt and glass insulator. Two tungsten filaments (both are C9 configuration, mounted in parallel) with 6 support hooks and a support attaching each lead to the stem. The stem assembly includes welded connectors, angled-dumet leads, and a mica heat-shield attached to the leads above the press. The shield clips are welded to the press. Lamp is filled with nitrogen gas. Tipless, G-shaped envelope with neck.
Hubble 2-prong electrical connector. Bakelite body and removable (2-piece) strain-relief. Relief screws into top of plug body. Two brass prongs in vertical configuration, contact screws. Indents near tip of prongs. Molded: "Patented / Knostrain" and "Hubbell".