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HFO Hall sensors



VEB Halbleiterwerk Frankfurt (Oder) produced a range of Hall sensor ICs. Many of these are copies of the equivalent Siemens Hall ICs. Some of these switches see use in keyboard switches. Following German reunification, at least some models appear to have remained in production under new ownership as Halbleiterwerk GmbH. The first models were introduced in 1981, with additional models following later in the decade. The original Siemens switches are likely to have been around in the early 1970s, as they will be what RAFI were using in the years before the HFO chips entered production.


Some models have a direct Siemens equivalent. Others do not.

Model Type Supply voltage Introduced TGL Siemens model
B 451 G Digital; dual in-phase outputs 4.75–27 V 1987 SAS 251
B 452 G 4.75–18 V SAS 251 S5
B 453 G 4.75–5.25 V SAS 251 S4
B 460 G Linear; dual outputs 4.75–18 V 1988
B 461 G Digital; single output, enable input 4.75–5.25 V 1981 TGL 38855, 1982 SAS 261 S4
B 462 G 4.75–18 V SAS 261
B 466 G Automotive ignition 4.75–12 V 1989
B 467 GA Linear; dual outputs 4.5–12 V

B 461 G

B 461 G is a small four-terminal Hall sensor. It is marked simply “B 61”, with the “4” and “G” omitted, supposedly due to the small component size (even though the full model name would have fitted).

The four terminals are:

  1. Masse (ground/GND)
  2. Ausgang (output) or offener Kollektorausgang (open collector output)
  3. Freigabeeingang (enable input)
  4. Betriebsspannung (operating voltage, VCC)

Unlike some other four-terminal Hall sensors used in keyboards (such as those of Micro Switch and Panasonic), B 461 G only provides a single non-redundant output. Instead, the fourth terminal is used to activate the sensor. Micro Switch’s type with enable input, however, used three

Usage in keyboards

Two companies are confirmed to have used B 461 G in keyboards. A Hall version of Sasse Series 25 is highly likely, but the choice of Hall IC is not confirmed. It is possible that they used Siemens ICs exclusively.


TGL 38855 specifies B 461 G as the Hall IC for RFT TSH 19 F keyboard switches. TSH (“Tastenschalter mit Hallelement”: keyboard switch with Hall element) was RFT’s Hall keyboard switch series. RFT TSH 19 F appears to have superseded TSH 19, which used a larger MH1SS1 Hall sensor from Czechoslovak manufacturer TESLA, itself appearing to be a copy of the Hall sensor used in Micro Switch SW Series.


B 416 G is or was also used in RAFI RS 76 C switches:

RS 76 C switches
View full-size image Part
View full-size image RS 76 C underside
View full-size image Part components

The above example—received as a sample from RAFI in 2016—uses a B 461 G chip apparently made in May 1991. This is indicated by the code “B5” at the lower right, per the Kodiertes Herstellungsdatum auf elektronischen Bauelementen aus DDR-Produktion (manufacturing date codes for East German electronic components).

Although this was a DDR chip, by 1991, VEB HFO had become Halbleiterwerk GmbH, as seen on the box label at eBay auction Lot of 5 pieces B461 = SAS261S4 HALL IC SWITCH static 4-SIP NEW *. RAFI did not comment on the age of the sample switches, and whether the switches are the same age as the chips, or if the chips are old stock. However, the indications seem to be that the production line is no longer open and the date sequence has thus not wrapped around to the subsequent year B (2001).