variable transformer
Date: circa 1970
Inventory Number: 2003-1-0168
Classification: Transformer
Subject:
Maker: General Radio Company (1915-present)
Cultural Region:
Dimensions:
20.5 × 13.8 × 15 cm (8 1/16 × 5 7/16 × 5 7/8 in.)
DescriptionThis device has two components: the box (a variable transformer capable of 110/140V) and the cable (with circuit breaker).
The box is a tall rectangular prism with a boxy metal handle connected to the sides. The top of the box features: toward the rear, a sticker (from Underwriters Laboratories) and two markings, near the middle, a number of screws holding the casing together, and close to the front, an outlet for a three-pronged plug and rubber grommet through which the cable emerges.
The rectangular faceplate of the box is connected to its front side by four screws, two in the bottom corners, and one on each side approximately two-thirds of the way up. In the top left corner of the faceplate is a switch that bears above it the word "ON". Next to this is the signature of the device which is partially covered by a faded white rectangular sticker that reads "TFGRA-1." The full signature can be read, however. In the top right corner is a red button that bears the letter "K" on it. Above this button is the label "RESET".
The bottom two-thirds of the faceplate are covered by a large black dial. The scale surrounding the dial is labeled "VOLTS OUT FOR / 120 VOLTS IN". The scale runs from 0 to 140 in increments of 10.
The cable that runs from the top of the box runs into a thick plug. The plug is made of several components, each made of a different component: the first, metal, the second, black rubber, the third, white plastic.
The box is a tall rectangular prism with a boxy metal handle connected to the sides. The top of the box features: toward the rear, a sticker (from Underwriters Laboratories) and two markings, near the middle, a number of screws holding the casing together, and close to the front, an outlet for a three-pronged plug and rubber grommet through which the cable emerges.
The rectangular faceplate of the box is connected to its front side by four screws, two in the bottom corners, and one on each side approximately two-thirds of the way up. In the top left corner of the faceplate is a switch that bears above it the word "ON". Next to this is the signature of the device which is partially covered by a faded white rectangular sticker that reads "TFGRA-1." The full signature can be read, however. In the top right corner is a red button that bears the letter "K" on it. Above this button is the label "RESET".
The bottom two-thirds of the faceplate are covered by a large black dial. The scale surrounding the dial is labeled "VOLTS OUT FOR / 120 VOLTS IN". The scale runs from 0 to 140 in increments of 10.
The cable that runs from the top of the box runs into a thick plug. The plug is made of several components, each made of a different component: the first, metal, the second, black rubber, the third, white plastic.
Signedon faceplate: VARIAC / AUTOTRANSFORMER / GENERAL RADIO COMPANY / CONCORD MASS USA
Inscribedon top of faceplate, in center: Type W5MT / VARIAC (R) / AUTOTRANSFORMER / GENERAL RADIO COMPANY / CONCORD MASS USA / ONE SIDE COMMON TO LINE AND LOAD / LINE 120 V 50-60 CYCLES LOAD C-140V 5 AMPS / US PAT 2949592
FunctionThe Variac adjustable transformer was introduced by General Radio in 1933. ("Variac" is short for variable AC.) It is an inductor, featuring a copper winding wrapped around a steel core. It is a tool used to attain a desired voltage (anywhere from 0 to 140 Volts). Its major use is to test equipment in order to see what range of voltage that equipment is capable of handling.
Curatorial RemarksThe patent mentioned on the instrument is found on the following website. It dates from 1960.