The forks have threaded shanks and will screw in the box tops. Frequency of each is A (426). One fork is fitted with a sliding mass to alter its frequency. On sounding both forks, a clear ‘beat’ is produced. Supplied with one hammer. Size of box 180 x 88 x 53 mm approx.

To demonstrate resonance, sympathetic vibrations and beat phenomenon. The two precision-made bars are mounted on a single solid resonance cavity. The cavity has two chambers with one bar tuned to 440 Hz, the other to 441 Hz. Includes: hammer and instructions.

To study the NAND digital logic gate and verification of the truth table.

A highly enlarged model, as seen under electron microscope, a portion of wall is removed to show ectoplast, endoplast, tonoplast, vacuoles, nuclear structure, plastids, mitochondria etc., mounted on base, with key card.