The system signalling medium can be Infra-Red or radio. The actual medium used is usually on the recommendation of the manufacturer, supplier or installer. Some manufacturers only produce radio based systems so infra-red will not be offered as an option. Many users are now more aware of the options available. Both methods of transmission medium have advantages and disadvantages. Use of Infra-Red as a transmission medium does not require any form of licensing, in any country. Radio transmission usually does require some form of licensing in most countries which is either a proven compliance to a specific standard of the country of use or a local individual site licence or both. Two of the most important safety features of remote control is the integrity of the signal processing system and watchdog features. Most COMMANDER systems incorporate high level 64 bit signalling to ensure that received and validated data is decoded and output correctly. This is carried out 10 times a second during the maintained command. Several incorporated watchdog safety features ensure that hardware is monitored and compared with received operator commands and when on standby, watchdog ensures that hardware is continually monitored. COMMANDER designs and manufactures both Infra-Red and radio systems. COMMANDER technology enables a combination of both mediums for specific application options.