The external AC power supply takes mains power and converts it to 12 VDC 5 A regulated power to supply power for the gang switch chassis, two external power supplies can be used to provide redundant power. Controller Cards take up only one slot, and external power connects to the controller card, One slot is reserved for future use, leaving you with 16 slots for A/B Switch Cards. All switch cards take up one slot except for the power A/B cards which take up two slots. Manage access to networks, implement backup systems for network and computer connections or share peripherals and other equipment. Local features include LED status and manual switching. Remote control (dry contact closure, RS232 and Ethernet) provides unmatched management flexibility. Gang Switch systems are used around the world to add secure access control and reliable backup for critical systems from space launch centers to stock exchange networks. Ordering instructions First, order the chassis... Gang Switch, 4U, 18-Card (SM960A) Next order at least one power supply (order two for redundancy)… External Power Supply 100- 240 VAC (SM961-PS) Internal Power Supply -48 VDC (SM760-PS1) Internal Power Supply Dual -48VDC (SM760-PS2) then select a Controller Card... Ethernet (SNMP) (SM962A) Logic Only (SM964A) ...next choose your A/B Switch Cards... Serial DBxx : DB25 A/B Non-Latching (SM965A) DB9 A/B Non-Latching (SM966A) DB15 A/B Non-Latching (SM967A) Power: 240 VAC 1 in 2 out (SM971) 120 VAC 2 in 1 out (SM973) Video: 75 ohm F-Connector (SM976A) Multimode: SC Latching (SM977A-SC) ST Latching (SM977A-ST) RJ45 Copper: CAT5e Non-Latching (SM978A) CAT6 Non-Latching (SM979A) This product works with: Power Supply (SM961-PS) A/B Switch Cards (SM965A, etc.)