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NEC's DSX™ is a compact, wall-mountable cabinet configured to support 4 CO lines, 8 digital extensions, and 2 analog lines with power failure. This system is one of the best small office PBX phone systems.
CompactFlash card interface (For IntraMail, software loading, and database backup)
Conference circuits, DTMF receivers and DTMF generators
NAND Flash for storing the system database
Battery for short term (14 day) backup of the internal Real Time Clock and station parameters
Two audio inputs for Background Music and Music on Hold (1/8 inch mono minijacks)
One audio output for External Paging (1/8 inch mono minijack)
Ethernet and USB ports for local and remote PC programming
RS-232 serial port for Station Message Detail Recording
(2) DSX Analog Door Box ports with associated relays
Built-in V.32BIS 14.4k BPS modem for remote maintenance
Even with all the value built into the basic off-the-shelf DSX-40, the system is easily expandable by adding station and line PCBs.