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Category 3 cable, commonly known as Cat 3, is an unshielded twisted pair (UTP) cable designed to reliably carry data up to 10 Mbit/s, with a possible bandwidth of 16 MHz. It is part of a family of copper cabling standards defined jointly by the Electronic Industries Alliance and the Telecommunications Industry Association. Category 3 was a popular cabling format among computer network administrators in the early 1990s, but fell out of popularity in favor of the very similar, but higher performing, Cat 5 standard. Presently, most new structured cable installations are built with Cat 5e or Cat 6 cable. Cat 3 is currently still in use in two-line telephone systems, and can easily be adapted to run VoIP (as long as you create a dedicated LAN for your VoIP telephone sets). While Cat 5 or higher is often recommended for VoIP, the reality is that the 10 Mbit/s bandwidth a cat 3 network can provide is far more than the 0.08 Mbit/s a VoIP phone needs at full load, and Cat 3 is even compatible with 802.3af PoE.
Note that unlike Cat 1, 2, 4, and 5 cables, Cat 3 is still recognized by TIA/EIA-568-B, its defining standard.
The newer 100BASE-T4 standard, which achieves speeds of 100 Mbit/s by using all 4 pairs of wires, allowed older Cat 3 based infrastructures to achieve a much higher bandwidth.
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Unshielded and shielded twisted pair cabling standards |
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- Cat 1: Currently unrecognized by TIA/EIA. Previously used for POTS telephone communications, ISDN and doorbell wiring.
- Cat 2: Currently unrecognized by TIA/EIA. Previously was frequently used on 4 Mbit/s token ring networks.
- Cat 3: Currently defined in TIA/EIA-568-B, used for data networks using frequencies up to 16 MHz. Historically popular for 10 Mbit/s Ethernet networks.
- Cat 4: Currently unrecognized by TIA/EIA. Provided performance of up to 20 MHz, and was frequently used on 16 Mbit/s token ring networks.
- Cat 5: Currently unrecognized by TIA/EIA. Provided performance of up to 100 MHz, and was frequently used on 100 Mbit/s Ethernet networks. May be unsuitable for 1000BASE-T gigabit ethernet.
- Cat 5e: Currently defined in TIA/EIA-568-B. Provides performance of up to 100 MHz, and is frequently used for both 100 Mbit/s and Gigabit Ethernet networks.
- Cat 6: Currently defined in TIA/EIA-568-B. Provides performance of up to 250 MHz, more than double category 5 and 5e.
- Cat 6a: Currently defined in ANSI/TIA/EIA-568-B.2-10. Provides performance of up to 500 MHz, double that of category 6. Suitable for 10GBase-T.
- Cat 7: An informal name applied to ISO/IEC 11801 Class F cabling. This standard specifies four individually-shielded pairs (STP) inside an overall shield. Designed for transmission at frequencies up to 600 MHz.
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| See also: TIA/EIA-568-B • Ethernet • 8P8C • Ethernet crossover cable • Twisted pair |
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