NRN Communication
Thanks to Nick Powell for this information
All track machines that have driving cabs were fitted with NRN to comply with (the then) BRB's commitment to the Hidden Report requirements, however as originally fitted the radios differed to those fitted in locos because there was a requirement for the radios to provide a possession management facility.
The project to fit radios to OTMs provided for every driving cab to have a radio, this included tampers, regulators, ballast cleaners, TRAMMs and Wickham Trolleys. The "Possession Management" requirement also caused radios to be fitted to tracklayers and cranes, although all crane radios had to be removed due to an interference problem with the safe load indicators. A special "portable" radio was developed for Wickham Trolleys by the Plant Dept at Ashford, so that all that was fitted to the trolleys themselves was a power supply point and a plate for a magnetic aerial.
Each cab was fitted with a "field" podium type radio (usually bolted to the floor between the cab seats), with a distant end box connected to the other cab radio, so that either radio could be answered from either cab, or 1 could be attuned to the NRN and the other tuned to a local possession frequency. (P&T machines, with 3 cabs, had an extra distant end box in the middle cab, and those TRAMMs with crane cabs also had an extra box).
"Field" radios have the capability of being dialled from any Railway phone, whereas loco radios can only be called using specialist equipment. It occurred to someone that for "attention" reasons, it wasn't desirable for OTM drivers to receive calls from all and sundry, and an order was issued that field radios were not to be fitted in driving cabs. So gradually (as they go for maintenance) the stock of field radios is slowly diminishing.
Machines purchased since 1998 have been fitted with Loco radios from new, additionally they have been of the Car Kit type, which are easier to deal with as they can be accommodated in the machine's driving consoles.
