[INOC-DBA] Re: Cisco IP phone power
Bill Woodcock
woody at pch.net
Mon Aug 18 19:38:39 PDT 2003
> Be aware that the AIR-PWRINJ has a power supply, but the part you
> quote doesn't, so you still need an external 48V power supply.
> This has caught more than a few people I know - check out the
> "External Power Supply" column of table 2 in the URL quoted.
> http://www.cisco.com/en/US/products/hw/wireless/ps430/products_data_sheet09186a00800f927d.html
Aaaaah! What were they thinking? Check table 1... It may be just that
the 350 comes with a suitable power supply, not that one isn't required.
Hm. This is a pain in the ass.
Okay, I've spent a bit of time looking into it, and I've digested a bunch
of documents and URLs below. I think what's actually needed is for us to
get our hands on a bunch of this hardware and check to verify what
actually woks and what doesn't. Now that 802.3af is actually ratified, a
lot of it should stabilize.
-Bill
_____________________________________________________________________
Description Cisco Aironet Cisco Aironet 350 Series
Power Injector Power Injector Single Port
Media Converter AIR 1100, 1200 Power Injector
Part Number AIR-PWRINJ-FIB AIR-PWRINJ2 AIR-PWRINJ
Wire Pairs 4 and 5 (neg) 4 and 5 (neg) 4 and 5 (neg)
7 and 8 (pos) 7 and 8 (pos) 7 and 8 (pos)
Electrical In: 48 VDC In: 48 VDC In: 48 VDC
-.380A -.380A -.200A
Out: 48 VDC Out: 48 VDC Out: 48 VDC
-.320A -.350A -.125A
(supplied by external powersupply)
Power Supply Cisco Aironet Cisco Aironet Cisco Aironet
Requirements power supply power supply power supply
or alternative or alternative or alternative
DC power supply DC power supply DC power supply
48 VDC + 5%, 48 VDC + 5%, 48 VDC + 5%,
18watts 18watts 9watts
_____________________________________________________________________
IP Phone Power Consumption
Cisco IP Phones capable of accepting in-line Power (the 79xx series)
can tell the switch they are attached to how much power they need.
This allows the Catalyst 6000 switch to allocate the correct amount
of power to the phone without over or under-allocating. Initially,
the switch does not know how much power a phone is going to need, so
it assumes it will need the user-configured default allocation. Once
the phone has booted up, it sends a CDP message to the switch with a
Type, Length, Value object (TLV) that contains information about how
much power the phone needs. At that point, the switch will adjust
its original allocation and return any remaining power to the system
for use on other ports. The following table shows power
requirements for each IP phone.
Phone Model Amps Requested Watts @ 42V
Cisco 7960 0.15A 6.30W
Cisco 7940 0.15A 6.30W
Cisco 7910 0.15A 6.30W
Note: Prior to the P003P301 load, the Cisco 7960 phones only
requested 5.04W of power, although the phones are capable of drawing
up to 6.30W of power. This can cause issues with customers who had
just enough power available before the upgrade to P003P301, having
some phones not come up after the upgrade because there was not
enough power available.
_____________________________________________________________________
The CiscoIPPhone can be powered by the following sources:
* External power sourceoptional Cisco AC adapter and power cord for
connecting to a standard wall receptacle.
* WS-X6348-RJ45V 10/100 switching moduleinline power provider to
the CiscoIPPhone when connected to a Catalyst 6000 family
10/100BaseTX switching module.
This module sends power on pins 1 & 2 and 3 & 6, which are also
used to transmit Ethernet signals. Before the switch sends power,
it tests for the presence of a CiscoIPPhone, avoiding damage to
other Ethernet devices.
* WS-PWR-PANELpower patch panel that allows the Cisco IP Phone to
be connected to existing Catalyst 4000, 5000, and 6000 family
10/100BaseTX switching modules.
This module sends power on pins 4, 5, 7, & 8, which are not used
for Ethernet signaling. Like the inline power, the power patch
panel also attempts to verify that the attached device is a
CiscoIPPhone before providing power.
* 48-port 10/100 Ethernet with inline power module for the Catalyst
4006 (WS-X4148-RJ45V)
* VoIP DC Power Entry module for the Catalyst 4006 (WS-X4095-PEM)
* External -48V DC power shelf common equipment for the Catalyst
4006 with two AC-to-DC PSU's and one empty bay for redundant option
(WS-X4608-2PSU) and the 110V 15A AC-to-48V DC PSU redundant option
for the power shelf (WS-X4608)
* Catalyst 3524-PWR XL switch (WS-C3524-PWR-XL-EN)
Power Source Design
The phone and switch automatically determine which power source the
phone uses. If the power has to be switched to a different source,
the phone user will experience different results based on which
power source is being used by the phone.
Use the following information to choose a power source for the phone:
* If you plug a phone into the optional power supply before plugging
it into the network, the phone is powered by the power supply.
* If you then unplug the phone from the power supply, the phone
resets. If the switch port is configured for 10/100 Mbps, the switch
recognizes the loss of power and brings the phone back up.
* If the switch port is configured for 10 Mbps only, then you must
unplug the network connection and plug it back into the phone for
the switch to recognize the phone's loss of power.
* If, however, you plugged the network connection into the phone
before you plugged in the power cord, the phone receives power
through the switch, and unplugging the power cord will not bring
down the phone. If the switch reboots, the phone will then be
powered by the power cord.
Redundancy Feature
For redundancy, you can use the Cisco AC adapter even if you are
using inline power from the Cisco Catalyst switches. Cisco IP Phone
7905G can share the power load being used from the inline power and
external power source. If either the inline power or the external
power goes down, the phone can switch entirely to the other power
source.
To use this redundancy feature:
1. Set the inline power mode to auto on the Cisco Catalyst switch.
2. Connect the unpowered Cisco IP Phone to the network.
3. Connect the external power supply to the phone after the phone
powers up.
_____________________________________________________________________
http://www.cisco.com/en/US/products/hw/modules/ps2797/products_tech_note09186a0080114add.shtml#first-sub2
http://www.cisco.com/en/US/products/hw/phones/ps379/products_tech_note09186a00801189b5.shtml
http://grouper.ieee.org/groups/802/3/af/
http://www.cisco.com/en/US/products/hw/wireless/ps430/products_data_sheet09186a00800f927d.html
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