Consisting of a self contained transmitter and receiver operating in the 40KHz region. Both transmitter and receiver are contained in separate plastic enclosures (60 x 100 x 25 mm) which contain the electronics and 9 V batteries. A special feature is the second output transducer on the transmitter.

Consisting of a self contained transmitter and receiver operating in the 40KHz region. The transmitter wave is modulated at a variable frequency of about 2KHz and is detected by the receiver which amplifies the signal and drives a miniature integral loudspeaker. Both transmitter and receiver are contained in separate plastic enclosures (60 x 100 x 25 mm) which contain the electronics and 9 V batteries. The receiver has 4 mm sockets so the output can be monitored on an oscilloscope for more quantitative measurements. A special feature is the second output transducer on the transmitter. This then becomes a twin coherent source and by moving the receiver, interference patterns can be dramatically demonstrated. The system is ideal for demonstrating sound waves above the hearing threshold and reflection properties associated with sonar etc. Complete with batteries.