Automatic transmission system

Lore & Background

Traditionally, radio and television stations were required to have a licensed operator, technician or electrical engineer available to tend to a transmitter at all times it was operating or capable of operating. Any condition that could interfere with other broadcast services would require immediate manual intervention. Because broadcast transmitters were often at a different location from the broadcast studios, attended operation required an operator to be physically located at the transmitter site. In the 1950s and 1960s, remote control systems were introduced to allow an operator at the studio to power the transmitter on or off. At the same time, an early remote control system, the Automon, was developed by RCA engineers in Montréal that included a relay system that automatically detected if the transmitter was operating outside of its allowed parameters. The Automon could send the studio an alarm if the transmitter was out of tolerance and, if contact to the studio was lost, it could automatically power down the transmitter. A similar system was developed in 1953 by Paul Schafer in California, using a rotary telephone to raise or lower transmitter parameters remotely.

As technology improved, transmitters became more reliable, and electromechanical means of checking and later correcting problems became commonplace. During the 1970s, the BBC made widespread use of automated systems on its UHF television network to switch from main to standby transmitters in the case of a fault, as well as to alert engineering staff to problems. In 1977, the U.S. Federal Communications Commission loosened operation rules to allow stations in the United States with ATSes to automatically monitor transmitter operation and allow the ATS to automatically adjust modulation or shutdown the transmitter if operation was out of tolerance, although the specific rules have continued to evolve with changes to the Emergency Alert System and the introduction of digital radio.

An ATS can also be used to automate scheduled tasks, such as lowering an AM radio station's transmission power at sundown and raising it at sunrise to meet license requirements for different propagation patterns at day and night. If anything goes wrong which the ATS cannot handle, it can send out calls for help, via pager, telephone voice message, or dedicated telemetry links back to a fixed point such as a broadcast studio.

Reader's Guide

The automatic transmission system represents a significant shift in broadcast engineering, moving from mandatory on-site human oversight to reliable unattended operation. The article describes how early remote control systems like the Automon and Paul Schafer's rotary-telephone system laid the groundwork for fully automated monitoring and correction. The BBC's adoption in the 1970s for UHF television networks demonstrated the system's ability to switch to standby transmitters and alert staff automatically. Regulatory changes in the United States in 1977 allowed ATSes to automatically adjust modulation or shut down transmitters when out of tolerance, a key step toward modern unattended operation. The system's scope is limited to the transmitter plant—it does not cover programming or studio equipment. Its legacy includes enabling broadcast stations to operate for long periods without direct human attention, while still maintaining compliance with technical standards and safety requirements. The ability to monitor conditions such as voltage, current, temperature, antenna ice, feedline pressure, and backup power sources, combined with automated alerts via pager or telephone, has made ATSes essential for modern broadcast infrastructure.

Did You Know?

• The Automon, an early ATS, was developed by RCA engineers in Montréal and could automatically power down the transmitter if contact to the studio was lost.
• In 1953, Paul Schafer in California developed a similar system using a rotary telephone to remotely raise or lower transmitter parameters.