Page 168 - Handbook of Electronic Assistive Technology

156 HANDBOOK OF ELECTRONIC ASSISTIVE TECHNOLOGY

of functional roles, although it would also be possible for these to be dispersed between
separate equipment modules. The functions of the controller may include some or all of
the following:
• Receive user selection commands, interfacing with the user’s ‘means of access’.
• Display the available EC functional options to the user. Display formats vary widely
in size and content magnification, colour versus monochrome, text and/or icons and
single or multiple menus of selection items. The unit is usually configured in a manner
bespoke to the individual user.
• Selection menu configuration settings.
• Configurations include type and speed of scan pattern, voice or other prompt options,
back light and standby timer.

Functions also include:
• Output control signal transmission.
• Feedback signal processing and modulation.
• Process and logic algorithms, which are discussed in Controller Mode of Operation of
Selection Process.

CONTROL TRANSMISSION SIGNALS
These transmit control signals to the controlled appliances, which with early systems
were by direct electrical cable connection and later progressed to IR and radio protocols
of various frequencies. For the second generation of ECS, proprietary radio signals have
been used, but latterly standardised protocols have been adopted, including DECT, WiFi,
Z-wave and recently Bluetooth.

FEEDBACK SIGNALS, PROCESSING AND MODULATION
Control modules of the EC system connected to certain appliances may provide feedback
to the controller of their status, which is displayed by the controller. The signal interchange
is therefore bidirectional.
In its simplest form, this is to indicate whether the appliance is on or off, but could
extend to different levels of operation. In the case of a remote paging or alert device, the
feedback information of interest is that the signal has been received satisfactorily by the
receiver and subsequently the alert has been acknowledged by the attending person.
In some instances this feedback may be used to modulate the control signals, for
instance to stop movement of a profiling bed if a travel limit is reached.
The status information conveyed as feedback can also relate to the status of inter-
nal componentry of the ECS itself to alert when attention is required or the system is
at the threshold of unavailability. Examples of such information include when the bat-
tery of the input device transmitter is about to become depleted or the input device has
become disconnected. Both are important states of operation, significant to maintaining
the user’s access to the functions of the ECS, including the ability to call for assistance.