Simply connect this revolutionary device into the target phone line ( with crocodile clips direct to the line)  or you can fit a BT plug and every time a phone on that line is used it will call a pre defined mobile telephone number of your choice  and  allow you to listen to the call in real time or record it automatically  on to a answer phone for example. The monitor uses the mobile telephone network to call the preset number and requires an operational SIM card inserting in it either contract or pay as you go. Measures 160 x 75 x 45mm