Communications, Data, and Audio/Video Distribution
Core concepts
Expect questions on structured cabling topology (horizontal, backbone, work area, entrance facility), the 100 m channel limit, and the roles of patch panels and cross-connects. Know twisted-pair pinouts (T568A and T568B), the need to keep both ends consistent, and how PoE classes deliver power over data pairs. Understand fiber basics: single-mode versus multimode, connector types, and why fiber suits long runs and electrically noisy environments. For audio/video, know balanced versus unbalanced signals, impedance matching for speakers (series/parallel and constant-voltage 70 V systems), and HDMI/HDBaseT distance limits.
Traps to expect
Questions often mix up A and B pinouts on one cable end, or assume a cable can exceed 100 m with a passive patch. Another trap is treating 70 V distributed speaker systems like 8 Ω home audio, or ignoring that PoE budget is shared across ports. Watch for items on balanced audio rejecting common-mode noise and on fiber not carrying power.
Worked example
Four 8 Ω speakers on one amplifier channel: two parallel pairs in series. Each parallel pair = 4 Ω; two pairs in series = 8 Ω total. The amplifier sees 8 Ω and delivers its rated power safely. Rule of thumb: keep total load at or above the amplifier's minimum impedance; use a 70 V transformer tap system when many speakers share one long line.