The wireless desktop intercom system connects up to 100 EXTENSION units. The communication range is 400 to m(1km), can cover up to 8 to 10 storey Building. This long range transmission is boosted by the 433Mhz frequency modulation which has no interference with our local frequency. The intercoms has internal battery backup as a provision and protection for our frequent power fluctuations and failure. The internal battery has the capacity and capability to power the system for over 24 hours without electricity. The battery life everything being equal is over 10 years.The detachable USB adapter and power cable technology allows a power bank emergency charging.This intercom system has already been programmed and coded with ID caller numbers. It is a plug and call system requiring no installation. It features multiple selectable ringing tones up to 38 selections and up and down volume level.The wireless desktop intercom system connects up to 100 EXTENSION units. The communication range is 400 to m(1km), can cover up to 8 to 10 storey Building. This long range transmission is boosted by the 433Mhz frequency modulation which has no interference with our local frequency. The intercoms has internal battery backup as a provision and protection for our frequent power fluctuations and failure. The internal battery has the capacity and capability to power the system for over 24 hours without electricity. The battery life everything being equal is over 10 years.The detachable USB adapter and power cable technology allows a power bank emergency charging.This intercom system has already been programmed and coded with ID caller numbers. It is a plug and call system requiring no installation. It features multiple selectable ringing tones up to 38 selections and up and down volume level.The wireless desktop intercom system connects up to 100 EXTENSION units. The communication range is 400 to m(1km), can cover up to 8 to 10 storey Building. This long range transmission is boosted by the 433Mhz frequency modulation which has no interference with our local frequency. The intercoms has internal battery backup as a provision and protection for our frequent power fluctuations and failure. The internal battery has the capacity and capability to power the system for over 24 hours without electricity. The battery life everything being equal is over 10 years.The detachable USB adapter and power cable technology allows a power bank emergency charging.This intercom system has already been programmed and coded with ID caller numbers. It is a plug and call system requiring no installation. It features multiple selectable ringing tones up to 38 selections and up and down volume level.The wireless desktop intercom system connects up to 100 EXTENSION units. The communication range is 400 to m(1km), can cover up to 8 to 10 storey Building. This long range transmission is boosted by the 433Mhz frequency modulation which has no interference with our local frequency. The intercoms has internal battery backup as a provision and protection for our frequent power fluctuations and failure. The internal battery has the capacity and capability to power the system for over 24 hours without electricity. The battery life everything being equal is over 10 years.The detachable USB adapter and power cable technology allows a power bank emergency charging.This intercom system has already been programmed and coded with ID caller numbers. It is a plug and call system requiring no installation. It features multiple selectable ringing tones up to 38 selections and up and down volume level.