This files most often as a second line on your mobile phone use the mode "Waiting". Before connecting it to your phone, make this service in your tariff plan. To do this, call your mobile operator for short technical support number and ask to activate "call Waiting". As soon as the operator will make changes in the plan – usually the service is free - you can start changing settings on the very phone.
To activate connected services "call Waiting" go to the mobile phone menu and click "preferences" or "Settings" depending on your model. Then find the function "Call", "Phone" or other similar function and check mode "call Waiting". Thus you have transferred the service to the active mode.
When, during the next conversation you hear a beep, look at the screen. If the display shows a message about the call of the second subscriber, click on the "answer" and start talking without interrupting the first call. The previous caller will listen to the standard music on hold.
If you want to connect second line to a landline phone, first check whether the apparatus of such a regime. Some older phones are not able to switch modes of conversation from one line to another. In the presence of such old models buy the new model in the cellular interior or the shop selling household appliances. Then contact the telephone company that provides you with telecommunications services on a landline phone. Bring certain documents, write a statement according to the sample and wait until processed according to the application will not be connected to the second fixed line.