HM Series Hermetically Sealed Basic Switch, Single Pole Double Throw Circuitry, 3 A at 28 Vdc, Integral Lever Actuator, Solder Termination MICRO SWITCH™ HM Series hermetically sealed basic switches contain contacts in a sealed chamber. A gas-tight seal is maintained while transmitting force and motion to the switch mechanism through a metal diaphragm. HM Series Hermetically Sealed Switches are not generally recommended for 115 Vac, 60 Hz. If you have a 60 Hz application in the mA range, or applications that require the switch to function electrically during exposure to sub-freezing temperatures, contact us for special design variations that are available.