ITT ETL18

ITT ETL18
Manufacturer	ITT
Switch type	Tactile
Sense method	Metal contact
Keycap mount	Proprietary cruciform
Switch mount	Plate mount
Patents	US4514609 A (1982)

ETL18 is a horizontal spring switch, or a series of such switches, from ITT.

Description

The name "ETL18" is taken from the branding on the top of the switch. A search for ETL18 at Oxygen Electronics (as of November 2016) returns two results: ITT ETL18 (depicted per other discovered ETL18 switches) and ITT ETL18H1X1GC.^[1] The latter may refer to a specific part in series ETL18, which would make sense as more than one product in the range is likely.

The switch is relatively large: the ridge that sits above the plate is 18 mm square, while the body is 16.3 mm square. Shell height is 13.6 mm, and the top of the mounting plate comes 11.6 mm above the top of the PCB. These non-DIN-compliant dimensions are curious for a German-made switch patented only a year before widespread adoption of DIN-compliant dimensions in 1983.

The keycap mount is proprietary cruciform; the switches do accept SMK keycaps made for SMK J-M0404 series switches. Cherry MX keycaps do not fit. The cross arms are the correct width to accept Mitsumi Commodore 64 keycap, but the slot widths within the keycap allow it to tilt on the keystem.

The switch features sealed terminals (with grey sealant instead of the typical red) and two recesses underneath to allow diodes to be placed below the switch.

Internals

The ITT switches are different from other internal spring-based key switches in that the spring is horizontally mounted through the key stem as depicted below. The dual metal contact fins appear to be for a dual pole switch but they connect to single contacts at each end of the switch. The tactile feel is provided by the internal Horizontal spring.

Testing with a multimeter demonstrates that the spring and contact arrangement does not provide hysteresis.

Variants

The switch has one known variant.

	Description
	Standard weight momentary

Keyfeel

The horizontal internal spring provides a tactile feel. The switch feels a lot like tactile Mitsumi miniature mechanical, but without that switch's rough feel. It lacks the tactile lead-in of the Mitsumi switches, however, with an immediate tactile peak that could possibly be described as "bouncy". While the Mitsumi switches drape the spring over a central hub, the ITT switches rely solely on a lateral buckling action of the spring to deliver a very smooth force curve.