Black Box Explains...Power over Ethernet (PoE).
Product Data Sheets (pdf)...Fluorescent and Flexible-Neck Lights
Product Data Sheets (pdf)...Fiber Blank for Module Rack
What is PoE?
The seemingly universal network connection, twisted-pair Ethernet cable, has another role to play, providing electrical power to low-wattage electrical devices. Power over Ethernet (PoE) was ratified by the... more/see it nowInstitute of Electrical and Electronic Engineers (IEEE) in June 2000 as the 802.3af-2003 standard. It defines the specifications for low-level power delivery—roughly 13 watts at 48 VDC—over twisted-pair Ethernet cable to PoE-enabled devices such as IP telephones, wireless access points, Web cameras, and audio speakers.
Recently, the basic 802.3af standard was joined by the IEEE 802.3at PoE standard (also called PoE+ or PoE plus), ratified on September 11, 2009, which supplies up to 25 watts to larger, more power-hungry devices. 802.3at is backwards compatible with 802.3af.
How does PoE work?
The way it works is simple. Ethernet cable that meets CAT5 (or better) standards consists of four twisted pairs of cable, and PoE sends power over these pairs to PoE-enabled devices. In one method, two wire pairs are used to transmit data, and the remaining two pairs are used for power. In the other method, power and data are sent over the same pair.
When the same pair is used for both power and data, the power and data transmissions don’t interfere with each other. Because electricity and data function at opposite ends of the frequency spectrum, they can travel over the same cable. Electricity has a low frequency of 60 Hz or less, and data transmissions have frequencies that can range from 10 million to 100 million Hz.
There are two types of devices involved in PoE configurations: Power Sourcing Equipment (PSE) and Powered Devices (PD).
PSEs, which include end-span and mid-span devices, provide power to PDs over the Ethernet cable. An end-span device is often a PoE-enabled network switch that’s designed to supply power directly to the cable from each port. The setup would look something like this:
End-span device → Ethernet with power
A mid-span device is inserted between a non-PoE device and the network, and it supplies power from that juncture. Here is a rough schematic of that setup:
Non-PoE switch → Ethernet without PoE → Mid-span device → Ethernet with power
Power injectors, a third type of PSE, supply power to a specific point on the network while the other network segments remain without power.
PDs are pieces of equipment like surveillance cameras, sensors, wireless access points, and any other devices that operate on PoE.
PoE applications and benefits.
Use one set of twisted-pair wires for both data and low-wattage appliances.
In addition to the applications noted above, PoE also works well for video surveillance, building management, retail video kiosks, smart signs, vending machines, and retail point-of-information systems.
Save money by eliminating the need to run electrical wiring.
Easily move an appliance with minimal disruption.
If your LAN is protected from power failure by a UPS, the PoE devices connected to your LAN are also protected from power failure.
Converters and Scalers Selector
IEEE 802.3 af
|PoE IEEE 802.3 at
|Power available at powered device
|Maximum power delivered
|Voltage range at powred source
|Voltage range at powred device
|Maximum cable resistance
Black Box Explains...Coax connectors.
Product Data Sheets (pdf)...LOCALMAP 100 Cable Tester
Product Data Sheets (pdf)...AntiStatic Service Kit and Wrist Strap
Product Data Sheets (pdf)...Crimp Tool
Product Data Sheets (pdf)...Power Meters
The BNC (Bayonet-Neill-Concelman) connector is the most commonly used coax connector. This large ”bayonet“ connector features a slotted outer conductor and an inner plastic dielectric, and it offers easy connection... more/see it nowand disconnection. After insertion, the plug is turned, tightening the pins in the socket. It is widely used in video and Radio Frequency (RF) applications up to 2.4 GHz. It is also common in 10BASE2 Ethernet networks, on cable interconnections, network cards, and test equipment.
The TNC connector is a threaded version of the BNC connector. It works in frequencies up to 12 GHz. It‘s commonly used in cellular telephone RF/antenna applications.
The N connector is a larger, threaded connector that was designed in the 1940s for military systems operating at less than 5 GHz. In the 1960s, improvements raised performance to 12 GHz. The connector features an internal gasket and is hand tightened. It is common on 2.4-GHz antennas.
The UHF connector looks like a coarse-threaded, big center-conductor version of the N connector. It was developed in the 1930s. It is suitable for use up to 200–300 MHz and generally offers nonconstant impedance.
The F connector is most often used in cable and satellite TV and antenna applications; and it performs well at high frequencies. The connector has a 3/8–32 coupling thread. Some F connectors are also available in a screw-on style.
The SMA (Subminiature A) connector is one of the most common RF/microwave connectors. This small, threaded connector is used on small cables that won’t be connected and disconnected often. It’s designed for use to 12.4 GHz, but works well at 18, and sometimes even up to 24 GHz. This connector is often used in avionics, radar, and microwave communications.
The SMC (Subminiature C) connector is a small, screw-on version of the SMA. It uses a 10–32 threaded interface and can be used in frequencies up to 10 GHz. This connector is used primarily in microwave environments.
The SMB (Subminiature B) connector is a small version of the SMC connector. It was developed in the 1960s and features a snap-on coupling for fast connections. It features a self-centering outer spring and overlapping dielectric. It is rated from 2–4 GHZ, but can possibly work up to 10 GHz.
The MCX (Micro Coax) connector is a coax RF connector developed in the 1980s. It has a snap-on interface and uses the same inner contact and insulator as the SMB connector but is 30% smaller. It can be used in broadband applications up to 6 GHz.
Product Data Sheets (pdf)...Data Taps
Cable Length Meter Manual
Manual for the CLM5000.