As soon as the handset is lifted, this recording system records both sides of the telephone conversation. Can be connected to any ISDN telephone line (1 line only). To make recordings of both lines, 2 recorders are required. If desired, the recorder can be hidden at ány point of the telephone cable. No personal interference is necessary except for changing the tapes from time to time. Powered by battery ór by 220 volt (adapter included).