Aviation Glossary - Telecommand

Telecommand

Telecommand is defined by the FCC as a one-way transmission to initiate, modify or terminate functions of a device at a distance [97.3(a)(43)]. If you are using a radio or wire line link to remotely control a station, this is "telecommand." The rules contain several requirements for remote control and telecommand operation:

Provision must be incorporated to limit transmissions to no more than three minutes if the control link fails. If the control link fails while your transmitter is keyed, the transmitter could be seriously damaged (not to mention the interference it would cause) if there was no three-minute timer to shut if off [97.213(b)]. But this also means that if the control link is functioning properly, there is no requirement for the station to have a three-minute "reset" or turn-off timer.
The station must be protected so that unauthorized transmissions cannot be made, whether deliberately or accidentally. This refers to providing safeguards on your remotely controlled station so it cannot be used by unauthorized operators. Most remote station licensees incorporate the use of DTMF tones or CTCSS systems to limit access to the control system to only those people who know the codes. You, as the licensee, are responsible for all transmissions from your remote station, just as you are responsible for your home station [97.213(c)]. This responsibility applies all the time, even if you share the control operator duties with other amateurs.
A photocopy of the station license and a label with the name, address, and telephone number of the station licensee and at least one designated control operator must be posted in a conspicuous place at the station location [97.213(d)].
Control (or telecommand) links may be wire (a telephone or fiber optic line, for example) or radio. The FCC says that if a radio link is used, the station where the control commands are performed is an auxiliary station [97.213(a)] and an auxiliary station is "an amateur station transmitting communications point-to-point within a system of cooperating amateur stations" [97.3(a)(7)]. All auxiliary operations must be conducted on appropriate frequencies 2 m and shorter wavelength bands, except the 144.0-144.5 MHz, 145.8-146.0 MHz, 219-220 MHz, 222.00-222.15 MHz, 431-433 MHz, and 435-438 MHz segments.

source: ARRL Ham Radio Glossary