NICET ITWBS Level III flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Delivered Audio Quality (DAQ)

A subjective 1-to-5 intelligibility scale used to grade public safety voice coverage; DAQ 3.0 is the usual minimum acceptance score for in-building systems, and DAQ 5 is near-toll quality.

Grid test

A coverage verification method using uniformly spaced test points across each floor, typically 20 to 25 points per floor, where the technician records DAQ and signal level at every point for acceptance.

Bi-directional amplifier (BDA)

An off-air repeater that amplifies donor signals in both directions to extend coverage indoors. Its usable gain is limited by donor isolation and available donor signal strength.

Fiber distributed antenna system

A system that converts RF to optical signals at a head end and distributes them over fiber to remote units and antennas, supporting multiple bands and sectors with centralized control.

Donor antenna

The antenna aimed at the outside macro site that links an in-building system to the public safety network; its placement and front-to-back ratio strongly affect isolation and leakage.

Donor isolation

The total path loss between the donor antenna and the service antennas. It must exceed system gain by roughly 15 to 20 dB to prevent feedback oscillation in the amplifier.

Leakage test

A measurement taken outside the building envelope, such as at the property line, to confirm the in-building system's signal stays below the AHJ threshold and does not interfere with the macro network.

Uplink noise rise

The increase in the donor site's noise floor caused by the in-building system's uplink amplification. Excessive uplink gain desensitizes the macro cell and is capped by carrier budget.

Service antenna

An indoor antenna that radiates and receives signals within the building; its type, placement, and downtilt determine coverage uniformity and leakage beyond the building envelope.

RSSI

Received signal strength indicator, a power measurement in dBm. Adequate RSSI is necessary but not sufficient for acceptance, because interference and delay spread can still degrade DAQ.

Simulcast overlap

A condition where two or more transmitters cover the same area with slight timing differences, producing distortion. In-building systems must avoid overlap zones that degrade DAQ.

Delay spread

The time difference between the first arriving signal and later multipath echoes. Excessive delay spread causes intersymbol interference and lowers DAQ even when signal strength is adequate.

Authority Having Jurisdiction (AHJ)

The organization, often the local fire department or building official, that adopts the code, sets acceptance thresholds for coverage and leakage, and approves the final test results.

Path loss

The reduction in signal power as it travels between transmitter and receiver, caused by distance, walls, floors, and materials; it is central to link budget and coverage prediction.

Link budget

A calculation summing transmit power, gains, and losses to predict received signal at the antenna. It determines whether the design meets the target signal level and DAQ.

Head-end equipment

The centralized electronics in a DAS, including the master unit, optical transceivers, and power supplies, that interface with the donor signal and manage distribution to remote units.

Remote unit

A distributed component in a fiber DAS that converts optical signals back to RF and feeds service antennas; remotes are placed throughout the building near coverage zones.

Donor site

The outside macro base station that provides the original public safety signal to the in-building system; its signal level, sector, and noise budget constrain the design.

Talkgroup

A logical channel grouping in a trunked radio system. Acceptance testing must use the actual subscriber radio on the actual talkgroup, since coverage varies by system configuration.

In-building coverage area

The defined interior spaces the system must serve, such as occupiable rooms, corridors, stairwells, and exit paths; the AHJ specifies which areas require coverage and at what DAQ.

Critical area coverage

Coverage required in high-risk spaces such as stairwells, elevators, and fire command centers, often specified at a higher DAQ or higher percentage than general occupiable areas.

Oscillation

Self-sustaining feedback in an amplifier caused by insufficient isolation between donor and service antennas; it raises noise, reduces gain, and can shut down the system.

Automatic gain control

A circuit that adjusts amplifier gain to maintain output level as input varies; it can mask isolation problems and must be understood when commissioning a BDA.

Composite power

The total RF power output of an amplifier across all channels, used to size components and verify compliance with rated limits and code requirements.

Coaxial cable loss

Signal attenuation in feedline, expressed in dB per 100 feet and increasing with frequency; it must be included in link budgets and antenna placement decisions.

Antenna front-to-back ratio

The difference in gain between an antenna's forward direction and its rearward direction; a high ratio improves donor isolation and reduces unwanted coupling.

As-built documentation

Final drawings and records reflecting the installed system, including antenna locations, cable routes, equipment models, and test results, submitted for AHJ acceptance.

Field test plan

A document defining test methods, grid spacing, DAQ scoring criteria, equipment, and pass/fail thresholds, agreed with the AHJ before acceptance testing begins.

Signal booster registration

A regulatory requirement in many jurisdictions to register installed BDAs with the carrier or licensing body, ensuring the system operates within licensed parameters.

Noise figure

The measure of noise added by a receiver or amplifier stage; a low noise figure in the first stage preserves uplink sensitivity and reduces required gain.

Public safety frequency bands

The licensed spectrum used by emergency services, commonly VHF, UHF, 700 MHz, and 800 MHz; the in-building system must support the specific band and channels in use.

Acceptance test report

The compiled record of grid tests, leakage tests, equipment data, and as-built drawings submitted to the AHJ to demonstrate the system meets the adopted code and design.