Using switches

What is a switch?

A switch is a device for making an electrical connection between two contacts.

Most of us use switches every day without thinking about it; for example when turning on a light, radio etc.

A simple way to understand how switches work with a computer is to consider switch software as being written to recognize a keyboard keystroke or mouse button press as a switch and so the aim of the switch interface is to enable switches to copy these. So, when a switch is used with a computer it is replacing a keyboard keystroke or mouse click.

How do switches work as an access method?

A switch can be used with pupils with severe and complex difficulties at different development levels. For example, it can be used to control a toy, light or simple computer program at a cause-and-effect level, where the pupil needs to press the switch (cause) to have a consequence or resulting action (effect). At a more advanced level pupils can use scanning to make choices. Scanning is a technique used with switches, in which a computer program highlights choices available for selection one at a time, allowing the pupil to make a selection by activating a switch when the item they would like to choose is highlighted. Scanning can be used by a switch user to make simple choices, e.g. from a choice of two items, to more complex forms of scanning which can allow a pupil to exercise complete control over the computer, i.e. the operating system and the programs.

Different types of switches available

There are now a wide range of switches available that vary considerably in design, function, reliability and functionality. Switches can be divided into two categories: contact switches and non-contact switches.

Contact switches

These switches require the pupil to make physical contact with the switch, using the part of their body which they can control most accurately, e.g. head, foot or hand. These switches are the most common and will meet most needs if firmly fixed in a position appropriate to the individual.

Switches can be seen to have a number of characteristics, that allow you to make judgements about their effectiveness for particular individuals, including:

Size – the target area a pupil has to hit to activate the switch
Travel – how far (if at all) does the switch move before it makes an activation
Pressure – the pressure required to operate the switch
Feedback – kinaesthetic (i.e. does the movement comes to an end when activated), auditory (an audible click can be heard), visual (colour and its contrast to the background it is going to be placed on) and tactile (does it have a recognizable tactile feel that is different to its background e.g. tray)
Mounting options – some switches come with fixing holes making mounting easier
Robustness – some pupils hit switches quite hard and so it is sometimes necessary to make sure that they are robust and able to withstand rough treatment

All these factors will affect how well a pupil uses a particular contact switch. Examples: AbleNet Jellybean switch; Tash Buddy Button switch; AbleNet BigRed switch; AbleNet Specs switch; QED lever switches; QED Pal Pads; QED Platform switches; Tash Micro light switch.

Non-contact switches Movement triggers these switches e.g. blink of the eye, tilt of the head, the making of a sound or the air movement caused by blowing or sucking. These switches are technically more difficult to set up and tend to require a higher level of understanding to operate than contact switches. Examples: QED Suck-Puff switch; QED Mercury Tilt switch; Toby Churchill Eye-Blink switch; QED Sound Operated switch

Scenario 1 – Choosing switches and switch position

First principles

Although there are a wide range of switches available on the market, experience shows that simple contact switches such as the Jelly Bean switch, BigRed switch and Buddy Button switch, will provide effective access for the majority of pupils with severe and complex needs. The important factor in ensuring that these switches are effective is to have them firmly fixed in the most appropriate position for an individual pupil. However there are individual pupils who will require a specialized switch to be able to gain effective control of it to allow development of their switching skills. A prerequisite to identifying an appropriate switch and switch position is to ensure that the pupil is positioned in a stable and functional position.

To establish the most appropriate choice of switch, its position and its mounting for a pupil, the professionals working with the pupil should have a good understanding of the equipment, how it is operated via a switch, the physical motor abilities of the pupil and how the technology can enable access to the pupil’s curriculum. This is best addressed by the combined expertise and knowledge of the pupil’s multidisciplinary team, e.g. teacher, occupational therapist, physiotherapist, speech and language therapist, parent and learning support assistant. There may need to be compromise between professionals to ensure the pupil is using the most successful method for them. When the best switch position has been established, the pupil is more likely to be motivated to develop their switching skills.

As the abilities of pupils with severe and complex needs may well change over time, it is important that the establishment of a switch position is not a one-off activity but is a continuous process of trial, monitoring, evaluating and modifying.

In most cases it is desirable to identify one switch position for a pupil with severe and complex needs which will be used to access a range of activities throughout the day. This allows the pupil to establish an effective motor pattern to operate the switch, that in time will ensure that the action of pressing the switch takes as little effort as possible and be as quick as possible, thus allowing the pupil to concentrate on the activity being controlled rather than the process of pressing the switch. However there are exceptions when a switch position may need to be varied; for example when the pupil’s tone changes from day to day or from hour to hour. In this situation there may be a position that is the most effective in the mornings but another that is more effective in the afternoons.

Positioning of the pupil

Effective seating and positioning often play a critical role in determining the success of switch use. Any seating or positioning equipment used should allow the pupil to concentrate on the activity under switch control and the movements required to make a switch activation, rather than on maintaining position and balance. The optimum position for switch use is achieved when the pupil can produce the movements required to activate the switch easily and with the least effort possible. The degree of support required to maintain a position is dependent on the pupil’s physical abilities; the involvement of the Occupational Therapist and / or Physiotherapist is essential in identification of appropriate seating and positioning equipment.

Example 1a

People working with Steven thought that his switch access was not particularly effective. During a review it was felt that Steven’s seating might be contributing to or causing this difficulty. The team agreed that a period of monitoring, during which Steven’s seating position should be varied, would be useful. Steven’s team realized that the chair was reclined at an angle throughout the day, despite the fact that in this position Steven’s functional control was limited. Putting the chair in a more upright position resulted in greater functional movement and consequently more effective switching. The team agreed to monitor this over time and review again in the future to enable them to reach a firm conclusion regarding the most effective seating position for Steven.

Key skills and equipment

The key skill is:

• the identification of an appropriate switch and switch position for a pupil

The key equipment is:

• team involvement
• supportive seating system

Positioning of resources

Ideally, equipment (e.g. monitor, toy, switch-operated device) should be directly in front of the pupil (except for pupils with visual field deficits) and at an appropriate height. It is recommended that equipment be placed on height-adjustable tables or trolleys to achieve this, particularly if the pupil is using several different seating and positioning systems.

Example 1b

Sue works in a number of different positions throughout the day. In the morning she often uses a standing frame, while in the afternoon she uses her supportive seating system. However, she needs to have access to her computer system at all times. This has been resolved through the use of a height-adjustable trolley.

Key skills and equipment

The key skill is:

• the identification of an appropriate switch and switch position for a pupil

The key equipment is:

• height-adjustable trolley

Identifying a switch and switch position

We want a switch that the pupil can operate quickly, when they want to, consistently and reliably, and that is the least tiring for them. The switch must allow the pupil to both activate it and release it with ease. The location of a rest position is as important as the location of the switch position. It might be helpful to get advice from your local Occupational Therapist or Physiotherapist, or both, on where best to position the switch. It is also important that the pupil is given the opportunity to express their opinion on the location of the switch, as experience shows that pupils, from an early age, often know the best movement to use.

• First you need to identify which parts of the body offer the best possibilities for reliable control. Identify which voluntary movement with that part of the body the pupil finds the easiest to control.
• Establish the area they can reliably target with this movement. This will determine the size of switch they need to use.
• Establish the strength of the movement, which will influence which switch you use. Have they got enough pressure to activate the switch they are using?
• Establish the best position of the switch in relation to the pupils’ body. The switch needs to be placed in the pupil’s range of movement for the voluntary movement identified, so it is easy and quick for the pupil to activate the switch.

Fixing the switch into place Once the best position is decided on, the switch should be firmly fixed, so that the pupil can be confident it will be where they expect it to be. There are several ways in which a switch can be firmly fixed into a position: Use Velcro. A Maxess board or a board covered in Velgrip material can provide a good surface onto which switches with hook Velcro on can be firmly fixed. If you make your own boards covered with Velgrip material they can be made to fit snugly into a pupils tray so that the board will remain in position. If angling a switch will ease access, the use of switch mounts will be beneficial. These fix to a Velgrip board and allow switches to be fixed to them with Velcro. In most situations, if the pupil is using their hand to activate the switch, angling the switch will make access easier; they can use one motor pattern movement to activate the switch and they will come off it with the aid of gravity. If the switch is flat they will be required to make one movement onto the switch and a second movement to move off.

If a switch needs to be mounted by a particular part of the body e.g. head, foot or knee, then a more sophisticated mounting system will be required. There are several mounting systems that are excellent to mount switches in various positions. They can attach to a table edge or the pupil’s chair or wheelchair. For some pupils, once the switch position is well established, a neater mounting system may be required; modular systems are available to achieve this.

Example 1c

In Mr B’s class, different pupils use different switches to access the computer. Through a process of assessing, implementing, monitoring and reviewing, the team working with the pupils in the class has found that: Rita’s most effective switch access method is through the use of a single large-contact switch mounted with a flexible arm mounting system. A single switch is used because it was found that Rita has only one very reliable and easy-to-produce movement. This switch is used because Rita needs a large target area and good feedback to confirm to her that an activation has been made. The mounting system is used because Rita’s most reliable and easiest movement for switching makes it difficult to mount a switch in any other way. It has also been noted that during the day Rita’s switching movement can change. The use of the mounting system allows for this. Bob uses two medium-contact switches mounted on angled wedges. This is because he has more than one reliable and easy-to-produce switch movement; when given the opportunity to use either a single switch with an automatic scan, or two switches with one switch to direct the scan and the second switch to make a choice (directed scan), it was found that Bob preferred the two-switch method – this gave him greater control.

Key skills and equipment
The key skill is:

• the identification of an appropriate switch and switch position for a pupil

The key equipment is:

• flexible arm mounting system
• large contact switch
• angled wedges with Velcro
• Velgrip board
• two medium-contact switches

Connecting switches

You may, at different times, and for different pupils, need to connect switches to battery devices, mains-powered devices or a computer. See Connecting switches on page 32 for more information about how physically to connect switch(es) to various devices.

Most switches now use a 3.5-mm plug and switch interfaces have 3.5-mm sockets. However you may have old switches in the school that have quarter-inch plugs; these can still be utilized with interfaces with 3.5-mm sockets by using a step-down adaptor. Similarly using a step-up adaptor you can use interfaces with a quarter-inch socket and switches with a 3.5-mm plug.

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