The Main or controlling KSU is shipped fully assembled. The following are included with the KSU: • CPU with main software (CPU-A1) • Power supply (110V/240V) • 1 External backup battery connector • 3 mounting spaces for 408E/008E/000E/1PRIU (3rd Slot of each KSU can not use for 4-Wire Multiline Telephone or DSS Console.) • 4 trunks + 8 hybrid Ext. I/F (408M-A1) • 1 power failure transfer circuit • 1 slot for EXIFB-C1 • 2 general purpose relay • SLT ringer • Message waiting lamp driver • One built-in answering circuit (VRS) The on-board DSP provides: • 20 telephony resources (DTMF/Dial tone/Busy tone/FSK caller-ID receiver/sender) • 128 tone sender resources (System tones sender/DTMF sender) • 32 ch conference resources