MIL-PRF-22710 Switches, Code Indicating Wheel \(Printed Circuit\), Thumbwheel And Push-Button, General Specification ForThis specification covers the general requirements for illuminated and non-illuminated, thumbwheel \(see 6.4.1\), and push-button, printed circuit rotary switches having unsealed and sealed modules and the associated hardware. These switches are designed for low power alternating current \(ac\) and direct current \(dc\) switching applications for use in electronic and communication equipment. Procurement of switches and mounting hardware will require additional data, giving detailed electrical and mechanical requirements, tolerances, and applicable additions and exceptions to the general requirements and tests specified herein \(see 6.2\).

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MIL-PRF-22710H

3.4.5.3 Contact alignment. Positive contact shall be made in all switch positions by contact engagement through

the longitudinal centerline of the stationary contacts in a plane normal to the switch module, stacked switch module

(see 6.4.5), or section.

3.4.6 Connectors. When specified (see 3.1 and 6.2), the printed circuit board shall be capable of mating with

applicable specification connectors (see 3.1).

3.4.6.1 Connector mating. Connector mating and unmating shall be accomplished without the use of special tools.

3.4.6.2 Connector retention. When connectors are furnished as part of the switch, the connectors shall be secured

to minimize any noise caused by physical movement of the connectors in the retaining tracks.

3.4.7 Lamp circuitry and illumination (when applicable, see 3.1 and 6.2).

3.4.7.1 Indicator ring. The indicator ring design shall permit the application of legends as applicable (see 3.1 and

6.2). The ring shall provide a black background with white markings, unless otherwise specified (see 3.1 and 6.2).

The contrast between the indicator ring markings and indicator ring background shall be nine minimum for switches

with a black background, and three minimum for switches with a gray background. Contrast shall be calculated in

accordance with the applicable requirements of MIL-DTL-7788, using the following formula:

Contrast = (brightness of marking) - brightness of background

brightness of background

The approximate ratio of character height to width of line shall be 8 to 1. For illuminated switches, the color for the

background or marking, as applicable, shall be provided by the use of a suitable color filter covering the lamp.

3.4.7.2 Lamp circuitry. Lamp circuits, when specified (see 3.1 and 6.2), shall be independent of the switching

circuits and shall be electrically isolated from the switch housing.

3.4.7.3 Lamp type. Illuminated switches shall use the lamp specified (see 3.1 and 6.2) for the illumination of the

indicator ring. For direct Government orders, lamps shall be assembled in the switch. Lamps may be omitted when

specified (see 3.1). Lamp failure shall not be considered a unit failure if, when the lamp failure is noted, a new lamp

is immediately installed and the lamp functions. Tests shall then be continued as required. However, lamp failure for

a nonreplaceable item (see 3.1) shall be considered a unit failure.

3.4.7.4 Lamp replacement. Lamp removal and replacement shall be accomplished without the use of special

tools.

3.4.7.5 Lamp contacts and retention springs. Lamp contacts and retention springs shall be suitably treated to

ensure conformance with established requirements.

3.4.7.6 Color. The color projected by the indicator ring for "clear" illuminated units shall meet the brightness

requirements (see 3.1). In those switches where red or white illumination is specified, red is any color for which y is

not greater than 0.335, and z is not greater than 0.002, in accordance with the coordinate system of the International

Commission on Illumination (C.I.E.).

The light transmitted through the white markings of the panel shall be provided by utilizing a clear, colorless filter with

a luminous transmittance of 0.90 (at 2365K) or no filters over the lamps or in the light assembly.

3.5 Contact resistance. Unless otherwise specified (see 3.1), when measured as specified in 4.5.2, the initial

contact resistance shall be not greater than 100 milliohms. Following moisture resistance test, and life (rotational)

test at atmospheric pressure, and at reduced barometric pressure (when applicable, unless otherwise specified (see

3.1 and 6.2.2), the value shall not have increased by more than 60 milliohms from the initial contact resistance

measurement value. Following the life, low-level switching test, the maximum contact resistance shall not exceed 1

ohm.

3.6 Circuit configuration. When switches are tested as specified in 4.5.3, the switch circuit configuration shall

conform to the applicable diagram specified (see 3.1 and 6.2). Switches shall make, carry, and break the required

circuits in all positions and in all sections, switch modules, or stacked switch modules.

3.7 Luminance (when applicable, see 3.1 and 6.2). When tested in accordance with 4.5.4, the photometric

brightness in foot-lamberts shall be as specified (see 3.1 and 6.2).