We are never told, but there are a few options:
The development of the "short-link" radio technology, later named Bluetooth, was initiated in 1989. Bluetooth is a standard wire-replacement communications protocol primarily designed for low-power consumption, with a short range based on low-cost transceiver microchips in each device.
In electronics, a remote control is a component of an electronic device used to operate the device wirelessly from a distance. For example, in consumer electronics, a remote control can be used to operate devices such as a television set, DVD player, or other home appliance, from a short distance. A remote control is primarily a convenience feature for the user, and can allow operation of devices that are out of convenient reach for direct operation of controls. In some cases, remote controls allow a person to operate a device that they otherwise would not be able to reach.
Radio control (often abbreviated to R/C or simply RC) is the use of radio signals to remotely control a device. Radio control is used for control of model vehicles from a hand-held radio transmitter. Industrial, military, and scientific research organizations make use of radio-controlled vehicles as well. In 1894, the first example of wirelessly controlling at a distance was during a demonstration by the British physicist Oliver Lodge.