A:Answer This is a regular consumer phone, if you have 4 phone lines (phone numbers), the phone will only recognize which line it is connected, if one KX-TS4200B is connected to 555-5555 and 555-5544 and another KX-TS4200B is connected to 555-5555 and 555-5533, when a call comes thru on 555-5555 both phones will ring. If unit 1 answers the call you can make a 2nd call on the other line, and then combine the calls to establish a conference call then unit 1 can hang up as soon as the other line answers to complete the transfer.
Simplest way to transfer the call though, is to press 'TRANSFER' during a call and press the speed dial (extension) button or enter the extension number, then place the handset on the cradle.