Why a remote at all
Early television sets needed frequent adjustment. Changing channels meant turning a dial or knob on the set, and fine-tuning, volume and sometimes picture settings required walking across the room. A remote control promised to save the trip, and it was one of the first consumer products to use wireless signaling in a household. The way the signal travels has changed several times, and each version was shaped by what electronics were affordable at the time.
Wired remote controllers
The first TV remotes were attached to the set by a cable. Zenith’s Lazy Bones, introduced around 1950, is the best-known example: a handheld box connected by a long wire to a motor in the set that turned the tuner. It worked, but the cable ran across the floor, and people tripped on it. The idea of wired remote controllers lasted only a short time on televisions, although wired remotes remained common for other equipment, from slide projectors to audio gear.
Light beams
The cable problem pushed designers toward wireless methods. In 1955 Zenith introduced the Flash-Matic, developed by engineers including Eugene Polley. It was a flashlight-like device that shot a beam of visible light at photocells on the television’s screen face. Different photocells controlled different functions, such as changing channels and turning the sound on and off.
It was wireless, but it had a flaw: the photocells reacted to any strong light, including sunlight or lamps, so the set could change channels by accident. Owners reported odd results when sunlight hit the screen.
Ultrasound
The next design avoided light. In 1956 Zenith introduced the Space Command, developed by Robert Adler and colleagues. Inside the handheld unit were aluminum rods of different lengths, and pressing a button made a small hammer strike one of the rods. Each rod rang at a different ultrasonic frequency, too high for most people to hear, and a microphone and tuned circuits in the television recognized which tone had been sent.
The device had no battery, since the energy came from the mechanical strike, and it was reliable. It was also noisy in a quiet room, because the click was audible. Other sounds could also cause trouble: according to common accounts, jingling keys or other high-pitched sources could trigger the set occasionally, and some pets reacted to the ultrasound. Later versions replaced the rods with transistor circuits, which required batteries but removed the clicking.
Ultrasonic remotes dominated televisions for roughly the next two decades, and many people of the era remember the click. The ultrasonic principle is a relative of the sound waves used in diagnostic ultrasound, although the purpose and frequency range were different.
Infrared and digital coding
Advances in semiconductors made another approach cheap. Infrared light-emitting diodes could produce a beam that people cannot see, and silicon chips could encode commands in a stream of pulses. Infrared remotes spread through the late 1970s and the 1980s, and became the standard.
The principle is simple. A chip in the handset scans the keys and, when a button is pressed, makes a specific code, a series of pulses and gaps. The pulses are usually modulated onto a carrier frequency in the neighborhood of 38 kHz, which helps the receiver distinguish them from steady background light, such as sunshine and ordinary bulbs. A detector in the television filters, decodes the pattern and carries out the command. Several manufacturers developed their own coding schemes, which is one reason why remote controls from different brands did not usually work with each other’s products.
Digital coding permitted many more functions. Instead of the handful of buttons on early remotes, a handset could include number pads for direct channel entry, menus, timers and, later, controls for videocassette recorders, disc players and cable boxes.
Universal and radio-frequency remotes
As homes filled with devices, people ended up with a pile of handsets. Universal remotes appeared in the 1980s. They stored codes for many brands, and some could learn the commands of other remotes by recording their infrared signals. Programmable remotes grew more sophisticated, with screens and macro commands that ran several actions at once.
Infrared has limits. It needs a line of sight, and it does not pass through cabinet doors or walls. Some systems therefore use radio signals, such as Bluetooth and proprietary radio-frequency links, which can work through obstacles. Smartphones can act as remotes using Wi-Fi or infrared, and voice assistants allow spoken commands. Many households now treat the remote as part of broader home automation. The moves from wires to light to sound to infrared and radio each followed what was practical and cheap at the time.
Summary of the stages
- Wired remote (about 1950): reliable, but the cable was a hazard.
- Light-beam remote (1955): wireless, but confused by ambient light.
- Ultrasonic remote (1956): no battery in the mechanical version, with its audible click.
- Infrared digital remote (from the late 1970s): coded pulses, many buttons, low cost.
- Radio-frequency, app and voice control: no line of sight needed.