HP vs Hurtz

The classic Hewlett Packard RPN (Reverse Polish Notation) calculators. - HP-35, HP-45. First pocket scientific calculators (1972).  - HP-21. 2nd gen of the HP-35 (1975)

Hurtz is a clean, precise audio tone generator. Dial in any frequency from 20 Hz to 20 kHz and hear it instantly — great for testing speakers and headphones, tuning instruments, or producing a steady reference tone. FEATURES • Any frequency, 20 Hz – 20,000 Hz, set by a slider or typed in exactly (with a log or linear scale). • Four waveforms: sine, square, saw and triangle. • Quick presets (100, 220, 440, 1k, 10k Hz). • Nearest musical note read-out with cents (A4 = 440), handy as a tuning reference. • Frequency sweep: glide smoothly from one frequency to another over a set time. • Stereo mode: set a different frequency on the left and right channels, with a live difference (Δ) read-out. Useful for stereo and channel checks, and for binaural tones (use headphones). • A live oscilloscope view of the waveform. • Adjustable volume, and a large play/stop control. • Works on iPhone and iPad. Everything runs on your device. The app has no ads, no accounts, no tracking, and no internet access — it collects no data at all. SAFETY Sustained high-volume tones — especially very high or very low frequencies — can be uncomfortable and may risk hearing or small speakers. Start at a low volume.