Air ultrasonic transceivers enclosed pulse transit type prowave 400ep18a a 18mm diameter 40khz ultrasonic transceiver of the standard enclosed type the back of the case is completely sealed with resin protecting the device from exposure to the environment enabling this transducer to be safely used in outdoor conditions as well as dusty indoor conditions the transceiver consists of a housing with an integral metal diaphragm the device operating at the resonant value of the first harmoni