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.
Solar power starts with the sun. This color lithograph is one of a set produced by Étienne L. Trouvelot (1827-1895) and published by Charles Scribner's Sons in 1881. “Solar Protuberances” is based on observations of the sun Trouvelot made on 5 May 1873. This particular lithograph was one of several used by traveling science lecturer Charles Came and later by his son-in-law Samuel Corby during public presentations given in the latter nineteenth century.
Generator for electric lighting system. This specimen utilizes seven elliptical-type field magnets designed to energize curved pole pieces on either side of a Siemens-type armature. A belt-drive coupling-wheel is used on the armature shaft. The field was personally designed by Wallace with the purpose of avoiding magnetic leakage. Hammer states that the machine was constructed on February 2, 1878, but wording in his article may actually refer to construction of the armature alone. Reference: Accession papers. Also William J. Hammer, "William Wallace and His Contributions to the Electrical Indus tires," Electrical Engineer, 1893.
Electric light machine. Nameplate reads: "Manufactured by Wallace & Sons, Ansonia, Conn." This electric light machine was constructed in November 1875, and was called the "Telemachon" by Wallace. It was exhibited at the Philadelphia Centennial Exhibition of 1876. A record in the Wallace & Sons shop stated that this dynamo was driven at a speed of 1000 RPM and supplied 11 arc lamps when driven by a 1.25" belt. One brush is missing from this specimen, and a pulley wheel is partly broken.
The original "Farmer" field contained two six-pole field magnets, each requiring six brushes. Wallace modified the field by connecting three poles together for one polarity, the remaining three for the opposite, thus making a two-pole field requiring only two brushes. This change increased the output of the machine. The armature is a Gramme ring, built up of thin sheets of iron, the plates being separated by paper. It is believed to be one of the first laminated armatures.
At a convention in Providence in 1891, Frank Sprague quoted an experiment at the Wallace Ansonia Plant, during which he observed this machine being run as a motor at two or three thousand RPM, and the rotational motion being stopped by a strong workman throwing his arms around the pulley. Sprague observed that both he and Wallace overlooked the fact that the total work done by the machine was actually equal to the torsional effort multiplied by the speed of the pulley rim. The device was also exhibited at the Franklin Institute Fair of 1884 and the Chicago World's Fair of 1893. Reference: William J. Hammer, "William Wallace and his Contributions to the Electrical Industries."
Telegraph sounders convert electrical pulses into audible sounds and are used to receive Morse code messages. The message travels as a series of electrical pulses through a wire. Short pulses make a dot, slightly longer pulses make a dash. The sequence of dots and dashes represent letters and numbers. The pulses energize the sounder’s electromagnets which move a lever-arm. The arm makes a loud “click” when it strikes a crossbar and the operator translates the pattern of sounds into the original language. A resonator like this was used to amplify the sound, making it easier for an operator to hear his or her own sounder when working in a room filled with these devices. This unit originally held two resonatod hoods though only one is left on the stand.
Generator for electric lights. Nameplate reads: " Manufactured by Wallace & Sons-Ansonia, Conn." This machine is an experimental generator built by William Wallace in 1877. A Pacinotti ring armature is used, mounted on a brass spider. The field magnets are stacked at two levels. The revolving armature has strip-type commutator segments. Copper wire brushes are used. A large pulley wheel is affixed to one end of the armature shaft. A portion of the wheel's circular area has broken off. Reference: William J. Hammer, "William Wallace and His Contributions to the Electrical Industries," 1893
Brass frame, carrying carbon plates 3" wide. Coils on top, not enclosed. Marked: "Wallace's patent December 18, 1877." Also, "92" stamped and etched on lamp. Carbon arc with 2 carbon plates. Regulator mounted on top.
Model for US Patent 203413, "Improvement in Armature for Dynamo-Electric Machines," issued 7 May 1878 to Charles F. Brush. A metal armature core with 8 slots for wire windings.
Painted label reads: "Gaume's / Electro-Magnetic Engine / Pat. Feb. 4, 1879, No. 524." The patent claims: "An arrangement of electromagnets and armatures whereby back pull upon the revolving magnets is avoided." A direct current motor housed in rectangular metallic case. The armature shaft has a commutator at one end with brush arrangement affixed to frame. Two binding posts are available for input voltage. The shaft runs through center of case to an L-shaped frame extension. Rectangular casing is decorated with painted floral designs and filigree. Reference: US Patent 211985, "Improvement in Electro-Magnetic Engines," issued to 4 February 1879 to Charles J. B. Gaume.
This telegraph register stamped with serial number 9092 was made by Knox & Shain, a noted Philadelphia maker of telegraph equipment. Telegraph registers are electrically-activated printers that receive Morse code messages. The message travels as a series of electrical pulses through a wire. The pulses energize the register’s electromagnets which move a lever-arm holding a pen or stylus. A clockwork mechanism pulls a strip of paper across the pen or stylus, recording the message. Short pulses draw or emboss a dot, slightly longer pulses a dash. The sequence of dots and dashes represent letters and numbers.
Alexander Graham Bell demonstrated several experimental telephones at the Philadelphia Centennial Exposition in 1876. This unit features a single electro-magnet and could be used both as transmitter and receiver. Bell approached the problem of transmitting speech differently from other telephone inventors like Elisha Gray and Thomas Edison. They were mostly experienced telegraphers trying to make a better telegraph. Bell's study of hearing and speech more strongly influenced his work.