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 includes a marble base and was made by Charles T. Chester of New York City. The electromagnet coils are fixed but the steel core can be moved to adjust the strength of the magnetic field.
A GE tubular heat-lamp, ca. 1975. Work on this product led to the invention of the tungsten-halogen lamp. Characteristics: Double-ended. Each end has a flat press, sheathed in metal (spot-welded joint) with a stranded-wire lead emerging from lower outside corner. C-8 tungsten filament with eleven disc-style supports (probably tantalum). The ends of the leads are threaded and the filament is screwed onto the leads. Tipless, T-shape quartz envelope. Note: 2000W lamps do not occur in the 1957, 63, or 65 catalogs. They do occur in the 1987 catalog, but with different lead structures.
Replica of a device made in 1821 by James Cumming (1771-1861, UK). A 8" x 4" base supports a 3-loop rectangular copper coil in the center of which is set a compass. Two brass mercury cups provide contacts for a battery. Reference: Chipman, Robert A. The earliest electromagnetic instruments. Bulletin of the United States National Museum. Contributions from the Museum of History and Technology 38, 123-135. Smithsonian Institution, 1964. https://repository.si.edu/bitstream/handle/10088/21310/USNMB-240_38_1964_472.pdf.
