Data, Communications, and Audio/Video Distribution
What this domain covers
Data, Communications, and Audio/Video Distribution tests structured cabling limits, cable categories, fiber and coax, PoE, and distributed audio and video. Expect TIA-568 and TIA-569 concepts plus practical field limits.
Core rules
- The horizontal channel is 100 m (328 ft): 90 m (295 ft) of permanent link plus up to 10 m (33 ft) of patch cords. The permanent link itself is limited to 90 m. Do not borrow patch-cord length by running 95 m of permanent cable.
- Category cable performance is not just a label. Cat 5e supports 1GBASE-T to 100 m; Cat 6 supports 10GBASE-T to about 55 m and 1G to 100 m; Cat 6A supports 10GBASE-T to 100 m. Shielded cable needs proper grounding and bonding.
- Fiber types: OM3 and OM4 multimode for shorter building and campus runs; OS2 single-mode for long runs. Connectors include LC, SC, and ST. Keep fiber bend radius generous, typically 10 times the cable diameter, and never look into a fiber or connector.
- Coaxial distribution is usually 75 ohm. RG-6 is common for CATV and satellite; F connectors must be installed with the correct strip length and torque. The shield is part of the signal path, not just a ground.
- Audio distribution often uses 70.7 V or 100 V constant-voltage lines. Add the tap wattages of all speakers on the line; the amplifier must have at least that capacity plus headroom. Check line loss and use the correct transformer tap.
- Video distribution: HDMI is distance-limited, especially passive copper; HDBaseT can extend HDMI over Cat 6 to about 100 m. Do not assume any Cat cable and any extender will work.
Worked example
A designer plans a 95 m permanent Cat 6 link plus 5 m patch cords at each end. The channel is 95 + 5 + 5 = 105 m, which exceeds the 100 m channel limit. The permanent link itself is also over 90 m. The fix is to shorten the permanent link to 90 m or less, or add an active extender or a fiber run. The reasoning is that the channel limit includes all cords, and the permanent-link limit is separate.
Traps that cost marks
Counting only the permanent cable; using copper-clad aluminum cable; mixing T568A and T568B pinouts; ignoring bend radius; overloading a 70 V audio line; and assuming HDMI cable length is unlimited.