Low Output Crystal Microphone by Unilab.Two of these Crystal Microphones can be used with the Unilab Fast Timer (B8H28573) to carry out the Speed of Sound Practical.The Microphone is not suitable by itself for producing a trace on an oscilloscope. In order to boost the signal so that a trace is seen the Microphone must be connected to an Oscilloscope via a Power Amplifier (B8R07696 or similar).Fitted with 90cm screened flex and two 4mm plugs.Pack Size: each