Burroughs HB-101 / MO-10 / 6700  
Written by Accutron on 2007-03-19  

Devices included in this entry:

Haydu 6700 unshielded MBST (pictured in thumbnail)
Burroughs MO-10 unshielded MBST
Burroughs 6700 unshielded MBST (red label variation)
Burroughs JAN-CBSC-6700 unshielded MBST


The 6700 is the first mass-produced beam switching tube, developed by Burroughs as a 2 MHz counter for use in computers. All subsequent beam switching tubes developed by Burroughs are direct descendants of the 6700.

While many beam switching tubes are intended for computer use, the 6700 is currently the only decimal counting tube of any type which is confirmed to have been used in the central processor of a commercially produced general purpose computer.

Haydu Bros. began mass-producing Burroughs tube designs shortly after they were acquired by Burroughs in 1954. The earliest Nixie and beam switching tubes have dual branding, with Haydu in the foreground and 'Subsidiary of Burroughs' condemned to fine print.

This inexplicable inversion of due credit still causes confusion to this day, as many sources either partially or completely credit Haydu with the development of these tubes, yet there is no evidence that Haydu was involved in their development at all. The earliest known advertisement for the Haydu 6700 states that the 6700 was perfected by the Burroughs Research Center, and mass-produced by the Haydu tube division. The extensive patent history of Nixie and beam switching tubes also supports this assertion, with all related inventors listed as assignors of Burroughs Corporation.

By 1957, the misleading Haydu branding was abandoned. As a result, the 6700 and low voltage variant 6701 are the only Burroughs beam switching tubes known to be branded as a Haydu product.

Burroughs 6700 Datasheet (PDF)
Criteria for Selection of the Magnetron Beam Switching Tube as a Circuit Component (PDF)
Beam Switching Tube Circuits for MBS Tubes Types 6700 - 6701 (PDF)


Haydu 6700 magnetic beam switching tube, serial number 28454. The earliest Haydu devices do not have a domed top cap. Instead, the top and bottom caps are identical.


Haydu 6700, black cap variation, serial number 34122.


Haydu 6700 carton, with Burroughs sticker affixed to the lid.


Extremely rare example of a Burroughs MO-10. The 6700 was only briefly sold under the MO-10 part number, and this is one of only a handful of surviving example of this variation.


Burroughs MO-10, serial number 2349. The chronological placement of the MO-10 is not yet confirmed. Its branding and cap configuration would suggest that the MO-10 falls between the Haydu 6700 and the red/black/white Burroughs 6700 pictured below, but the four digit serial number may suggest otherwise.


Burroughs 6700, black/red/white variation. A slightly later variation retains the red printed label, but has a different print arrangement and a black bottom cap like later bare iron variations.


Burroughs 6700, serial number 53340.


Early Burroughs 6700 carton with matching red, black and white.


Burroughs 6700, bare metal silver print variation.


Burroughs JAN-CBSC-6700, a military variation.

This article is part of the [Beam Switching Tubes] exhibit.

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