Audio systems. A microphone converts sound pressure into a small voltage; that signal is amplified (gain), processed, and eventually driven to a loudspeaker with enough power to move air again. Gain structure (or gain staging) is the discipline of setting levels correctly at every stage of that chain so the signal is strong enough to stay above the noise floor, but never so strong it clips or distorts. Set gain too low early in the chain and you amplify noise along with the signal later; set it too high and you introduce audible distortion or feedback — the howling loop that happens when a microphone picks up its own amplified output from a nearby speaker.
Impedance matching between a source (microphone, DI box) and destination (mixer input, amplifier) affects both signal quality and safety for the equipment — professional audio gear is typically designed around standard low-impedance mic inputs and higher-impedance line-level connections, and mismatches show up as weak signal, hum, or distortion.
Video systems. Video signals travel over several standards: composite and component (older analog formats), and HDMI, DisplayPort, and SDI (digital, used almost everywhere in modern courtroom and conference-room installs). Each has its own maximum cable length, bandwidth, and connector type — HDMI is common for shorter runs, while SDI (used heavily in broadcast and courtroom recording) tolerates much longer coaxial cable runs before signal degradation.
Resolution (e.g. 1080p, 4K) and aspect ratio (16:9 is now standard; older systems used 4:3) determine how an image is displayed; a technician must ensure source, distribution equipment, and display all agree, or handle scaling and EDID (Extended Display Identification Data, the handshake a display uses to tell a source what resolutions/formats it supports) to reconcile mismatches.