Erlang meaning

Erlang is a measure of call traffic used in telecommunications contracts, service level agreements (SLAs) and regulatory reporting to specify and price network capacity. It expresses the average number of simultaneous voice calls (or equivalent channels) carried over a stated period, typically the busy hour. One Erlang equals one fully utilised circuit for the whole measurement window; fractions represent partial utilisation. For example, 30 Erlangs over one hour means an average of 30 concurrent calls. Although widely referenced in Ofcom and ComReg contexts, Erlang is an engineering unit rather than a term defined by UK or Irish legislation or case law; usage is consistent across England & Wales, Scotland, Northern Ireland and Ireland. Legal significance: it underpins capacity planning, service levels and service credits, wholesale trunk and SIP capacity commitments, and contact centre outsourcing (often via Erlang B/Erlang C queuing models and agreed grade of service or blocking probabilities). Contracts should define the measurement period, data source, averaging methodology and exclusions (for example, short calls or test traffic), and specify any busy-hour assumptions, to avoid disputes.