Kitchen sink disposals typically have a momentary (push-button) switch for activation rather than a traditional on/off switch. When you press the switch, it sends a signal to start the disposal, and it remains activated as long as you continue to hold the switch down. Once you release the switch, the disposal automatically turns off. This design allows for more control over the operation and ensures that the disposal operates only when needed, typically for a short duration ranging from 15 to 45 seconds, as you mentioned.