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Micro Switch 1SW200 Series


1SW200 Series is a hypothetical designation for a subseries of Micro Switch SW Series. So far, only two switches are known from this subseries, which are both bi-level (double-action).


Only two models are presently known. Both contain the same sensor type (“U”) and the same spring. The only observable difference is that one is sloped and one is stepped. While they still follow the odd–even numbering rule, the catalogue listing numbers are not adjacent.

Catalogue listing Action Output Plunger colour Plunger style
1SW201-R Double action (bi-level) Unknown Black Sloped
1SW204-R Double action (bi-level) Unknown Black Stepped

These bi-level switches are externally identical to standard momentary switches. The sensor package has the same form factor, and the extra springs are fully contained within the switch.

View full-size image 1SW204-R and 1SW201-R


1SW200 bi-level switches have three springs: the standard return spring, and two additional springs retained within the plunger. These additional springs rest on a pair of brass pins.

View full-size image 1SW204-R (stepped) and 1SW201-R (sloped) plungers, side views
View full-size image Side view of the 1SW201-R plunger, showing the high-force springs and associated pins
View full-size image 1SW201-R plunger showing both barium ferrite magnets

When the switch is in the free position, the pins are raised above the switch mounting frame. As the plunger is depressed, the pins are lowered onto the mounting frame. This first stage has a light feel. From this point on, depressing the plunger further requires compressing all three springs, as the pins can not move further. The second stage requires a considerable amount of force to actuate, as is standard with double-action switches.

Travel is increased from around 4.75 mm to around 6.2 mm. The first stage comes to a stop after 3 mm when the pins for the stage two springs strike the mounting frame. The second stage has another 3.2 mm of travel. The bottom of the plunger is slightly shorter as a result, to increase the switch travel sufficiently.

View full-size image 1SW51-R and 1SW201-R plungers
View full-size image 1SW51-R and 1SW201-R plungers

There is also a small difference in the shell. Two internal vertical wedges—of unknown purpose—were removed to make room for the spring assembly on the back of the plunger.


The bi-level sensors are marked with type “U”. This type also occurs in SD Series, but the only documented example suggests that “U” within that series has a different meaning, as it seems to be used for the A key.

View full-size image Two 1SW51-R sensors (“A”, back and front views), and “U” sensors from 1SW204-R (front) and 1SW201-R (back)

These sensors have a taller IC die than normal, with two separate Hall elements. This allows them to detect two different actuation depths with a single sensor package. The sensor still has four terminals; instead of dual redundant outputs, there are non-redundant outputs for each of the two stages. The current mode of the sensor (current sink or current source) is not known.