How to switch between Standard scanner and Alternative scanner?

Pre-requisite:

App version 4.19.0

Step 1: 

To access the menu, tap on the 3 line menu icon located at the top left and the menu will show. 

Tap on Settings.

Step 2:

To select camera, slide the button to the left as shown below.

Step 3:

Select Alternative Scanner to make it the default scanner.