The T18U series U-GAGE® opposed mode ultrasonic Emitter/Receiver Pairs. They utilize an advanced built-in microprocessor to analyze the received ultrasonic signal and control an indicator LED located on the back of the receiver. The receiver LED flashes at a rate proportional to the received sonic signal strength. This indicator greatly simplifies sensor alignment and alerts personnel to marginal sensing conditions due to gradual misalignment or environmental factors. The receiver is precisely tuned to the ultrasonic emitter, making this sensor pair highly immune to both sonic and electrical ambient noise. T18U receivers may be wired for either of two resolution modes, NORMAL or HIGH. Opposed mode ultrasonics are very useful for highly reliable sensing of clear materials, which is always a challenge for photoelectric modes. The acoustic face of both emitter and receiver are epoxy-reinforced for extreme durability and moisture resistance.