Alan,
It sounds like you're talking about a CTCSS, or
'tone squelch' accessory. If so, then, no, it doesn't
do anything with range or signal strength. It's just
a way of turning off reception of any signal that doesn't
have the 'tone', sort of like having a private line instead
of a party line with telephones. The tone is like a 'key'
that will open the 'door' to another radio that's using a
'tone squelch' so they don't have to listen to everything
else on a channel.
'Doc