Switch Access and Scanning: Getting Started

Switch access lets someone operate an AAC system with one or more simple buttons — called switches — instead of touching the screen directly. It opens AAC to people who cannot reliably point, touch, or use eye gaze, including many people with significant physical disabilities. The device highlights options one at a time, and the user presses a switch to choose. This is called scanning, and a few settings make the difference between a system that feels effortless and one that feels exhausting.

What a switch is

A switch is any button the user can reliably activate with a part of the body they control well — a hand, head, foot, cheek, or knee. Switches plug into the device or connect over Bluetooth (a switch interface adapts wired switches for tablets). The right switch and the right mounting position are as important as the software settings, and an occupational therapist or SLP can help find the best access point.

One switch or two?

• One-switch (automatic) scanning: the highlight moves on its own through the options, and the user presses the switch to select the one that is highlighted. This needs only a single reliable movement, but relies on timing.
• Two-switch (step) scanning: one switch moves the highlight to the next option, and the second switch selects it. This removes the timing pressure and gives the user full control of the pace, but needs two reliable movements.
• Some users start with two-switch step scanning to learn the cause-and-effect, then move to one-switch automatic scanning as it becomes automatic.

Scan patterns

The scan pattern is the order in which the device highlights items. The most common is row-column scanning: the highlight steps down the rows, the user selects a row, then the highlight steps across that row to the item. Row-column is much faster than linear scanning, where every cell is highlighted one at a time. Larger grids almost always use row-column (or block) scanning to keep the number of steps manageable.

The settings that matter most

• Scan speed (scan rate): how long each item stays highlighted before moving on. Start slow and speed up only as the user gets faster — too fast is the most common cause of frustration and mis-selections.
• Acceptance time (switch acceptance / debounce): how long the switch must be held before it counts, which filters out accidental bumps and tremor. Increase it if selections fire by accident.
• Auto-restart and number of scan loops: how many times the highlight cycles before pausing, so the user is not stuck if they miss a pass.
• Audio cues (auditory scanning): the device can speak or beep each option as it is highlighted, which lets users with limited vision scan by ear.

Where scanning settings live

• TD Snap: open Settings, then Access Methods (or Switch Access / Scanning) to choose scan pattern, speed, and the number of switches.
• Grid 3: open Menu, then Settings, then Access, then Switches — set the scan style, timing, and how each switch is mapped.
• TouchChat / Proloquo2Go: scanning lives in the app’s own settings (look for Access or Scanning), separate from the device’s system-wide switch control.
• iPad system-wide: Settings, then Accessibility, then Switch Control lets a switch drive any app, including AAC apps that do not have their own scanning.

Build the skill gradually

Scanning is a learned skill. Many users begin with cause-and-effect activities (one switch that makes something fun happen), then a single large target, then a two-item choice, and only later a full grid. Celebrate activations, keep early targets motivating, and give plenty of time — pushing the speed or grid size too soon is the fastest way to discourage a new switch user.

Setting up switches on a specific app or device? Open the chat, tell it your device and how many switches you have, or attach a screenshot of the access settings, and it will walk you through the exact taps.