ID:
2697
Dimensions:
8 × 7.5 × 7.5 cm
An indicator to show the actual frequency of a mains electricity source operating at nomimal 50 Hz.
A row of metal reeds with white flags on their end sits in the oscillating magnetic field produced by two coils. Each reed is weighted to oscillate naturally at a different frequency and when driven by the magnetic field the resonant one has a larger amplitude that is visible in the front panel.
