With Australian Telstra phones, if you called someone and they didn't pick up after a number of rings, a carrier tone would happen. If you whistled a handshake,

With Australian Telstra phones, if you called someone and they didn't pick up after a number of rings, a carrier tone would happen. If you whistled a handshake, the reciever would PICK UP and yes you literally turned it into a hot mic. Since I no longer have a landline, I can't confirm it works now.