Scenario 8 - Recording switch use

So that everybody working with the pupil is familiar with their method of access and the level they are working at, it may be useful to have an information sheet like the example on the next page. Also, a photograph (perhaps digital) can be particularly helpful to show the correct switch position.

It is important that progress is recorded, monitored and evaluated. At the early stages of switch development there is often no record of their work, but screen shots of the software being used or digital photographs of them using an electrical appliance etc, could be printed and placed in their record of achievements.

Example 8a

The team working in Class 5 is aware of how switches are positioned for individuals, and for which activities the pupils in the class use their switches. Photos were taken of all the pupil’s switch positions, and placed within records kept in the classroom. New staff working in the classroom are shown the records, and mounting systems are demonstrated if necessary. Appropriate activities are also included in the records.

Key skills and equipment
The key skill for the above example is:

• the ability to use a camera (digital or other) to record switch positions

The key equipment is:

• camera, recording system

Switch recording sheet (PDF file - 4 k)

Connecting Switches

Using a switch with battery-powered devices

A switch can control any battery-powered device with a single on / off switch by connecting a battery device adaptor.

It is recommended that an adaptor be connected to each individual device. This means the device is always ready for use with a switch and ensures the adaptor leads last longer.

Battery tips – although NiCad rechargeable batteries often seem a good idea, be aware that they can lose capacity over time, as they are discharged and recharged. Alkaline batteries might give better value, but you may also consider NiMH rechargeables; these are more expensive and require a special charger, but last much better than NiCads.

Fitting an adaptor to a device

If there is a lid over the battery compartment, use a file to notch a groove in the lid to prevent it pinching the wire.	Insert the battery adaptor's contact disc between the battery and one of the battery contacts. Close the lid.
Plug the switch into the battery device adaptor and turn the device's on / off switch to its 'on' or 'play' position.	The user activates the switch to turn the device on.

Connecting a switch latch / timer unit to a battery-powered device

Using a switch to control electrical appliances

To control a mains-powered appliance with a switch, it must be linked through a control unit. The control unit ensures safety by isolating the switch from the mains voltage.

Never try to switch mains current directly.

The control unit

Some examples of suitable control units are described in the Appendix 4. The units vary in power rating (wattage). The electrical appliance used should not exceed this wattage, as this would be unsafe, and a fuse would be blown in the control unit. If driving more than one appliance at a time, take account of the total power rating.

Although the switch itself is entirely safe (it is isolated from the mains), it is important to remember that the lead to the appliance from the unit should be kept out of reach of the pupil, as this is at mains voltage.

Modes of control

All the control units have a selection of operating modes. These include:

Momentary or direct: The appliance will operate for as long as the input switch is pressed.

Timed: The appliance is switched on when the user presses the input switch, and switches off after a preset timed period, regardless of what the user is doing with the switch.

Latched: The appliance is switched on and off with alternate switch presses.

Connecting switches to a computer

When you are using switches with a computer, the switches will usually work as though they are sending keyboard presses (usually ‘Space’ or ‘Enter’) or sometimes mouse clicks. So most switch software will allow you to use the standard keyboard or mouse to operate it, as well as switches. This can be very useful if you want to try out the software without connecting switches – or sometimes to work alongside a pupil.

To use switches with a computer, some kind of interface to connect the switches is required. There are essentially three different types:

• keyboard switch interface – PC or Mac
• mouse switch interface – PC or Acorn
• serial switch interface – PC or Acorn

Keyboard switch interface

This method of attaching switches is the standard throughout the world. Common interfaces are the Don Johnson Switch Interface or IntelliKeys (an overlay keyboard with switch sockets). More recently available devices are the SwitchBox (a programmable keyboard switch interface) and SwitchBoard (a standard keyboard with switch sockets).

Don Johnston switch interface	Intellikeys with switches attached
SwitchBox - a programmable switch interface	SwitchBoard with switches attached

Mouse switch interface There are interfaces that connect through the mouse port, such as the Mouser, or a special mouse or roller that has switch sockets built in (such as the Inclusive KidTrac). You should note that not all switch-accessible software will allow mouse clicks for the switch action, so this solution will not work for all switch access. However, mouse-switches can be especially useful in the situation where a carer / peer moves the mouse pointer and the pupil presses the switch to select. Alternatively you may have a pupil who can manage to move the pointer, but needs to hit a bigger target than a mouse button (i.e. the switch).

Serial switch interface This is usually a small box which connects to the serial port of the computer. The box has (usually) two switch sockets. A software driver will cause the switches to emulate key presses. This driver may be an integral part of the program you are using, or may be a separate program. This is the least expensive option, but can be the least reliable. Historically it has been the most common way of attaching switches in the UK. But as more software from other countries is now localized for use here, it becomes a less viable option.

Selecting a switch interface

Before selecting an interface box, you need to ensure compatibility with the switch software you intend to use. For example, not all switch software will give the option of using mouse buttons, which is required if you are using a mouse interface. Some software does not offer the option of using switches through a serial interface box.

It is recommended that professional advice is sought in identifying the most appropriate switch box for your school computers. See Unit B – Organizing your resources for more information.

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