Retevis RT638 Walkie-Talkies 1 pair @ RetevisDirect FBA

• RT638 walkie talkie for kids is safer; with 16 channels and 121 private codes avoids receiving other strange signals and keeps the child safe

This is NOT a security setting and does NOT mean you can have private calls, it does not keep kids safe.

If this setting is enabled, you don't hear other poeples calls, as your radio is looking for a specific audio subtone tone to that tells your radio to output the sound from the speaker.
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If someone else has a a radio and NOT turned on the CTSS tones feature they will hear everything you transmit.

Range is likely to be a few hundred meters at most in most urban enviroments.

Can you turn the beep noise off?

I don't know if it helps you but these apparently have a VOX mode which means there's no need to use the push to talk. They'll transmit when they hear sound meaning you can set and forget, assuming it works well enough.