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Chapter 10 • Assistive Technology Integration and Accessibility 301

but to provide a framework for considering an integration model that may be appropriate
for a specific individual.

Dedicated Integrator Unit or Device-Switching Model

This is one of the more ‘traditional’ models of integration and is essentially as described
by Hawley et al. in 1992. This approach still has relevance and advantages for some users.
Integrating in this way requires an additional, external, integrator unit – this unit directs
the input signals (e.g., switch signals) from one device to another (Fig. 10-1). To direct the
signals, the user will have to control the integrator – either via a specific operation of the
input (e.g., long switch press) or through an additional ‘mode’ switch input. The advan-
tages and disadvantages of such systems are listed in Table 10-1.
In Selina’s case (see Selina’s Case Study section) the benefits of this model are that
she is able to have distinct controls for each device. Head mouse for computer, using sip-
puff for mouse clicks. Switching using sip-puff and sip-puff for EC scanning. The system is
simpler to set up and will default to the EC system if the power or battery in the integrator
fails – ensuring that Selina is still able to call for attention in these situations.
This mode requires either a custom-made integrator unit or one of the few commercial
7
units available such as the CSS ClickMan (Fig. 10-2).
Primary/Secondary Pass-Through Model
In this case the user has a primary device that they use as their main device – i.e., they use
it for most of the day or in most situations of importance, (Fig. 10-3). Through this device
they are then able to access a secondary and potentially third device. The primary device
is acting as the integrator in this model.
This model can be realised in different ways:
1� The input is ‘passed through’ the primary device and will be sent back to control the
primary device after a timeout, or through the use of a mode switch. Although there
are now few assistive devices that support this mode, this mode does describe Apple’s
‘Platform Switching’ feature.
2� The input is used to send a range of other signals from the main device to the
secondary device. For example, the control method of the main device (e.g., a switch)
could be used to send mouse navigation commands or text output via infrared.

The benefits and disadvantages of this model are listed in Table 10-2.
Wheelchair as Base Model

This is a variant of the primary/secondary device model (Fig. 10-4).

7 https://www.csslabs.de/cms/index.php/de/component/k2/item/52-clickman-adaptiver-multicontroller-
fuer-einfachsensoren.