Instructions for Modifying a Mouse
for Connection of Single Switches to a Computer

Before undertaking this task, read the following instructions and determine your comfort level with proceeding. An alternative to modifying a mouse is purchasing a modified mouse. Purchase Modified Serial - PS/2 Mouse. Purchase Modified USB Mouse.

Start by acquiring a mouse that is compatible with the computer to be used. Be prepared to know if you want a mouse that can be used with a PS/2 port, a serial port, or a USB port. A mouse can be purchased for under $10 at many different kinds of stores. Look for a mouse that has enough room to add the switch jacks.

Start by confirming that the mouse is working properly by connecting it to your computer and, if necessary, installing the driver. Then disconnect the mouse from the computer.

Next acquire two mini mono phone jacks. A mini phone jack is the size to accept a standard earphone or headphone plug that is about 1/8” (3.5 mm) diameter. This jack is the size to accept the plugs of the most common assistive technology switches. Radio Shack Catalog #274-248 is a bag of two jacks and as of October 2004 had a price of $2.99.

If you don’t have the basic tools for doing this work, you may need to borrow or purchase them.

Power hand drill or drill press
¼” drill bit
Solder iron and solder
2 ft. #22 or smaller gauge insulated stranded wire
Small screwdrivers
Small needle-nose pliers
Wire cutter
Wire stripper

Caution: For all of this work use proper techniques and safety procedures to avoid injury, especially when drilling holes and soldering.

Open the mouse. This is generally done by removing screws that may be on the bottom of the mouse. Adhesive sliding pads may need to be removed if some of the screws are under them. Be careful not to lose the screws and other small parts since they will be needed later when the mouse is reassembled.

Identify the switches that are activated when the left and right mouse buttons are pressed. They may look like small boxes with a button that can be pressed to make it click. The switches generally have terminations that go through the circuit board and are visible on the bottom of the board, which will need to be removed for this step.

If one of the terminations on one switch is connected electrically to a termination on the other switch, this is the connection that is now to be called COMMON. The printed wiring can be followed from one switch to the other to make this determination. If there is a COMMON termination, it will be the one that will be wired to the sleeve or threaded connection of the switch jacks that will be added to the mouse.

Identify places on the mouse where there is enough room inside to accommodate the jacks. If possible, try to have the left button jack on the left side of the mouse, and the right one on the right. Otherwise, they can be labeled. Mark those places and drill ¼” holes.

Mount the jacks. If there is a COMMON termination in the mouse, wire the two jacks together so that the sleeves (threaded parts) are connected. Connect wires from the jacks to the switches.

If possible, test the modified mouse before reassembly by connecting it to the computer.

Reassemble the mouse, being careful to locate the new wires so that they do not interfere with the original mouse operation.

Feedback is welcome. If you encounter difficulty or have suggestions for improving these instructions, please forward to:

An alternative to the above procedure is to purchase a modified mouse from AAC Institute or other sources or to ask someone with the appropriate skills to perform the modification.