AT Switches are used to allow people with difficulty controlling their environment to trigger electronics. They are commonly used to control Speech Generating Devices and toys that have been modified to be “switch adapted”.
Technically, they are generally Single Pole Single Throw (SPST) momentary switches that are terminated in a two conductor (mono or Tip/Sleeve) 3.5mm or 1/8″ audio plug. Most are physical switches meaning current can flow either direction and common low-voltages and currents are supported (12V, 500mA are common).
If you’ve never seen an AT switch in action, here’s a great video of Max Lasko using two AT Switches to control a Scout that ATMakers made for him.
Common vendors include Ablenet, Enabling Devices and more.