
These secret settings are basically designed for the developers or testers so they can easily check out the functionality of the operating system and whether devices are working fine or not some hidden dialer codes also provide you some shortcuts for settings like call divert, call waiting, call forwarding, etc.
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Suppose you’re going to purchase a second-hand device and want to make sure that everything is working fine on that device then you can also use these settings to check sensors, display, colors, signal strength, etc. features.