A radio recovery receiver and transmitter used for when the crawler has broken down due to an electrical fault and will reverse the crawler out of the pipe.
The units operate on the 433Hz band and can be set to 16 frequencies (channels) within that band.
The radio transmitter and receiver are supplied as matched sets which do not require any further set up in normal use. If for any reason it is necessary to change the operating frequency or 'match' transmitters/receivers not supplied as sets, there are two sets of 8 pole DIL switches in each unit which can be set to 16 different frequencies (note transmitter and receiver must be set on the same frequency). This is what prevents transmitters interfering with other receivers operating on the same channel.