|Year: 1948 ??||Type: Recorder and/or Player|
|Valves / Tubes||3: 6SL7GT 6SN7 6X5|
|Wave bands||- without|
|Power type and voltage||Alternating Current supply (AC) / 110 Volt|
|Loudspeaker||- only for Earphone!|
|from Radiomuseum.org||Model: Mail-A-Voice BK-503 - Brush Development Co.;|
|Shape||Tablemodel, with any shape - general.|
|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.
Model page created by Ernst Erb. See "Data change" for further contributors.
All listed radios etc. from Brush Development Co.; Cleveland, Ohio
Here you find 38 models, 34 with images and 21 with schematics.