FEATURES 10-25M, 25-75M & 75-150M External Ranges. No Hardwire Synchronisation. Integral Head Heaters. High Power Transmission. Graded Alarm Responses. Slimline Housings Fog Detection Output. Four Step Alignment. Sixteen Beam Paths.   CONCEPT. The Rednet series of active infrared photobeams is a range of detection devices for both internal and external applications. The system utilises the infrared transmission to synchronise transmitters and receivers & removes the need for hardwire connections between towers. This feature greatly reduces installation time & cost. An automatic graded alarm response system uniquely combines the ability to provide high levels of detection with a low potential for false alarms.   OPERATION. The RN4 10-25m, 25-75m, & RN4 50-150m comprises four transmitters & four receivers which can be housed within either a free-standing or wall mounted tower enclosure. The towers are of an ultra-slimline design & provide a full 180 degree unobstructed view for the beams. This results in Rednet fitting into all system configurations with ease. Tower enclosures RLW 175 and RLT 175 are constructed from aluminium and acrylic with all fixings being stainless steel. This ensures that housings remain both functional and attractive throughout their installed life.   GRADED ALARM RESPONSE. Rednet graded alarm response is a technique to reduce false alarms whilst maintaining security levels. The system monitors the sixteen individual beam paths & when an object bigger than the distance between the beam heads is detected a beam response time of 40 milliseconds is employed. If a single beam is broken the system automatically sets the required beam break time to 500 milliseconds or more. This dual response reduces the likelihood of the beams responding to small animals or blowing debris whilst still offering protection against a crawling intruder.