{"openapi":"3.1.0","info":{"title":"AC Resonance & Reactance API","version":"1.0.0","description":"AC reactance and LC/RC tuning maths as an API, computed locally and deterministically. The reactance endpoint computes the capacitive reactance Xc = 1/(2πfC) and the inductive reactance Xl = 2πfL at a given frequency, and — when both a capacitor and an inductor are supplied — the net series reactance X = Xl − Xc, whether the circuit looks inductive, capacitive or resonant, and the impedance magnitude. The resonant endpoint computes the LC resonant frequency f₀ = 1/(2π√(LC)), or, given a target frequency and one component, solves the other component you need to tune to it. The cutoff endpoint computes the RC or RL filter cutoff frequency — fc = 1/(2πRC) for RC, fc = R/(2πL) for RL — and the time constant. Frequencies are in hertz; capacitance, inductance and resistance accept SI base units with handy µF/nF/pF and mH/µH inputs. Everything is computed locally and deterministically, so it is instant and private. Ideal for electronics, RF, audio-filter and embedded app developers, tuning and filter-design tools, and electronics education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is AC reactance & LC/RC tuning; for LED series-resistor sizing use an LED-resistor API and for VSWR and impedance match use a VSWR API.","contact":{"name":"PremiumApi","url":"https://www.oanor.com/by/premiumapi"}},"servers":[{"url":"https://api.oanor.com/resonance-api","description":"oanor gateway"}],"tags":[{"name":"Resonance"},{"name":"Meta"}],"components":{"securitySchemes":{"oanorKey":{"type":"apiKey","in":"header","name":"x-oanor-key","description":"Get your key at https://www.oanor.com/developer/keys"}}},"security":[{"oanorKey":[]}],"paths":{"/v1/cutoff":{"get":{"operationId":"get_v1_cutoff","tags":["Resonance"],"summary":"RC/RL filter cutoff","description":"","parameters":[{"name":"resistance","in":"query","required":true,"description":"Resistance (Ω)","schema":{"type":"string"},"example":"1000"},{"name":"capacitance_uf","in":"query","required":false,"description":"Capacitance (µF) for an RC filter","schema":{"type":"string"},"example":"1"},{"name":"inductance_mh","in":"query","required":false,"description":"Or inductance (mH) for an RL filter","schema":{"type":"string"}}],"security":[{"oanorKey":[]}],"responses":{"200":{"description":"OK","content":{"application/json":{"example":{"data":{"note":"RC filter: fc = 1/(2πRC), τ = RC. Same fc for low-pass and high-pass.","inputs":{"capacitance_f":1.0e-6,"resistance_ohm":1000},"filter_type":"RC","time_constant_s":0.001,"cutoff_frequency_hz":159.154943},"meta":{"timestamp":"2026-06-04T18:38:10.322Z","request_id":"c72aee63-d8b8-4b0b-ab49-0ed8546a369e"},"status":"ok","message":"Filter cutoff","success":true}}}},"401":{"description":"Missing or invalid x-oanor-key header"},"402":{"description":"Active subscription required"},"429":{"description":"Rate-limit or monthly quota reached"},"502":{"description":"Upstream did not respond"}}}},"/v1/reactance":{"get":{"operationId":"get_v1_reactance","tags":["Resonance"],"summary":"Reactance at a frequency","description":"","parameters":[{"name":"frequency","in":"query","required":true,"description":"Frequency (Hz)","schema":{"type":"string"},"example":"1000"},{"name":"capacitance_uf","in":"query","required":false,"description":"Capacitance (µF)","schema":{"type":"string"},"example":"1"},{"name":"inductance_mh","in":"query","required":false,"description":"Inductance (mH)","schema":{"type":"string"},"example":"10"},{"name":"capacitance","in":"query","required":false,"description":"Or capacitance (F)","schema":{"type":"string"}},{"name":"inductance","in":"query","required":false,"description":"Or inductance (H)","schema":{"type":"string"}}],"security":[{"oanorKey":[]}],"responses":{"200":{"description":"OK","content":{"application/json":{"example":{"data":{"note":"Xc = 1/(2πfC), Xl = 2πfL. 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