Voice over IP (VoIP), it is the wave of the communications future. My company converted about two years ago from traditional phone lines. Goodbye Ma-Bell, hello Cisco. VoIP phones like the
Cisco 7940 IP Phone need an IP address in order to take and make phone calls, but they also need power. And in order to supply (DC) electrical power over a category 5 cable the phones have to be connected to a network switch that supplies a reliable source of DC power like the
Cisco Catalyst 3570-PoE network switch.
Note: Power-over-Ethernet (PoE) or "Active Ethernet" eliminates the need to run 110/220 VAC power to Wireless Access Points and other devices on a wired LAN such as IP Phones. Utilizing PoE system installers need to run only a single CAT5 Ethernet cable that carries both power and data to each device. This allows greater flexibility in the locating of Wireless Access Points AP's and network devices and significantly decreasing installation costs in many cases.
Power-over-Ethernet begins with a CAT5 "Injector" that inserts a DC Voltage onto the CAT5 cable. The Injector is typically installed in the "wiring closet" near the Ethernet switch or hub. We use our complement of some 100 Catalyst 3750-PoE switches to power and connect our installed base of IP Phones.
In turn the
Cisco Catalyst 3570-PoE switch needs a reliable source of DC electrical power, that is where the
Cisco Redundant Power System 675 (RPS 675) comes into the picture. The small 1U rack mount unit is in effect a (backup) power supply designed to provide internal power supply redundancy for up to six Cisco networking devices and provides those devices with an immediate failover capability. If the internal power supply of one of the connected Cisco Catalyst 3570-PoE switches were to fail the
Cisco RPS 675 automatically senses the failure and delivers uninterrupted power to that device. This in turn guarantees uninterrupted VoIP service for the enterprise.
According to Cisco product literature
"[T]he Cisco RPS 675 can be combined with the Cisco Catalyst 3750 and 3560 inline power switches and uninterruptible power supply (UPS) systems to establish all of the elements of the Cisco Centralized Power Provisioning System. This combination provides a resilient, highly available converged network, offering 1) internal redundant power to the switch; 2) power to the IP phone via the switch's inline power feature (rather than wall power); and 3) back-up in the event of a power outage."
The
Cisco RPS 675 provides (6) 675W DC outputs to various Cisco devices through rather thick gray cables. The
Cisco RPS 675 has two output levels: 㫈 VDC with a maximum output of 375W and 12 VDC with a maximum output of 300W, for a maximum total output power of 675W. The -48V mode powers telephone systems in line-powered switches like the
Cisco Catalyst 3570-PoE switch.
The front of the
Cisco RPS 675 is pretty much unadorned. There are six DC output LED status lights on the far left hand side of the unit; other LED's show the status of internal power, fans, and temperature. There is also a Standby/Active button.
The rear of the
Cisco RPS 675 is dominated by the (6) 16-pin DC output connectors. To the far right sits the fan exhaust, and to the far left sits the AC power connector. The unit ships with a single a single 1.2-meter (48-inch) 16-pin-to-14-pin connector cable which connects the DC output connector to an external device. Additional cables have to be ordered separately for an average cost of $60.00 each.
Cisco RPS 675 Use
Typical deployment of the
Cisco RPS 675 finds one unit in each wiring closet per floor supplying redundant power to up to (6)
Cisco Catalyst 3570-PoE switches. And each of our branch location have one installed a well. So far the units have proved themselves highly reliable; we have yet to have a
Cisco RPS 675 and have to be replaced.
The only downside of the
Cisco RPS 675 is the size of the DC connector cables, which may make installation troublesome.
Conclusion
In today's technology rich environment, where VoIP is becoming the norm a reliable source of DC power is a must. The
Cisco RPS 675 can and does provide that internal redundant power for our complement of
Cisco Catalyst 3570-PoE switches.
