Switches can be used with battery-operated or electrical devices to give people with disabilities a way to participate in activities, control their environment, or even just play and discover cause & effect for the first time.
A switch works like an on/off button. Connecting it to a
battery-operated toy or electrical appliance lets a person safely and
easily turn the item on or off.
There is a tremendous variety of switches for people with limited
motor skills or other disabilities: push, tilt, pull, latch, blink,
sip & puff, etc. Have an OT help you choose best switch, and
position, for the individual.
The diagrams below show how to hook up a switch to a battery-operated
device or to an electrical appliance.

This diagram shows a switch (1) plugged into a switch latch &
timer (2), which in turn is plugged into a copper battery device
adapter (3). Insert the copper wafer into the battery compartment
between any two contacts. You may need to file the edge of the
compartment door to avoid pinching the cable when you latch the
door.

This diagram shows a switch (1) plugged into a PowerLink (6) which
also has a blender (5) plugged into it. The Powerlink unit must be
plugged into the wall. The dial on the Powerlink allows you to adjust
the amount of time an appliance will play following one press of the
switch.