Mail-A-Voice BK-503

• Country
• United States of America (USA)

• Manufacturer / Brand
• Brush Development Co. / Clevite Electronic Components; Cleveland, Ohio

• Year
• 1948–1950

• Category
• Sound/Video Recorder and/or Player

• Radiomuseum.org ID
• 129443

• • alternative name: Brush Electronics

• Picture
• Schematics

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Click on the schematic thumbnail to request the schematic as a free document.

• Number of Tubes
• 3

• Valves / Tubes
• 6SL7GT 6SN7GT 6X5GT

• Main principle
• Audio-Amplification

• Wave bands
• - without

• Details
• Other Recorder/Player

• Power type and voltage
• Alternating Current supply (AC) / 60 Hz: 110-120 Volt

• Loudspeaker
• - only for Earphone!

• Material
• Metal case

• from Radiomuseum.org
• Model: Mail-A-Voice BK-503 - Brush Development Co. /

• Shape
• Tablemodel, with any shape - general.

• Dimensions (WHD)
• 300 x 140 x 280 mm / 11.8 x 5.5 x 11 inch

• Notes

• The model BK-503 Mail-A-Voice from "The Brush Development Company", represents an entirely different approach to the problem of storing information on a magnetic medium. The recording material in this case is in the form of a 9-inch disc, and the sound track is a spiral running from an inner diameter of 5 inches to the outer edge. The recording track has a width of 0.014 inch, and the pitch of the spiral is 0.025 inch. Despite this close spacing, no noticeable crosstalk can be detected. The powder-coated paper discs can be folded and mailed like an ordinary letter. No guide grooves are provided on the coated discs.
  
  The turntable rotates 20 r.p.m., resulting in a total recording time of slightly over 3 min. This instrument deserves special mention because it presently represents the most simple and basically the most inexpensive mechanical and electrical design for a magnetic recorder that has been produced commercially. A single crystal headphone is used both as a recording microphone and as a playback earphone.

  See also the combination with the SWISS Repondomat as a telephone answering machine. The Mail-A-Voice model BK-503 might have existed one or two years before 1948. But for us only 1948 to 1950 is for sure.

• Net weight (2.2 lb = 1 kg)
• 6.5 kg / 14 lb 5.1 oz (14.317 lb)

• Author
• Model page created by Ernst Erb. See "Data change" for further contributors.

• Other Models

• Here you find 43 models, 39 with images and 22 with schematics for wireless sets etc. In French: TSF for Télégraphie sans fil.
  All listed radios etc. from Brush Development Co. / Clevite Electronic Components; Cleveland, Ohio