# Automatic transmission system

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Not to be confused with [automatic transmission](/source/Automatic_transmission).

An **automatic transmission system** (ATS) is an [automated](/source/Automate) [system](/source/System) designed to keep a broadcast radio or television station's [transmitter](/source/Transmitter) and [antenna system](/source/Antenna_(radio)) running without direct human oversight or attention for long periods. Such systems are occasionally referred to as *automated transmission systems* to avoid confusion with the [automatic transmission](/source/Automatic_transmission) of an [automobile](/source/Automobile).

## History

Traditionally, radio and television stations were required to have a licensed [operator](/source/Operator_(profession)), [technician](/source/Technician) or [electrical engineer](/source/Electrical_engineer) available to tend to a transmitter at all times it was operating or capable of operating. Any condition (such as [distorted](/source/Harmonic_distortion) or [off-frequency](/source/Frequency) transmission) that could interfere with other broadcast services would require immediate manual intervention to correct the fault or take the transmitter off the air. Facilities also had to be monitored for any fault conditions which could impair the transmitted signal or cause damage to the transmitting equipment.[1]

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.[1] 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.[2] A similar system was developed in 1953 by Paul Schafer in California, using a rotary telephone to raise or lower transmitter parameters remotely.[3]

As [technology](/source/Technology) improved, transmitters became more reliable, and [electromechanical](/source/Electromechanical) means of checking and later correcting problems became commonplace. [Regulations](/source/Regulation) eventually caught up with these advances, to allow of unattended operation via an ATS.[1] During the 1970s, the [BBC](/source/BBC) made widespread use of automated systems on its [UHF](/source/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.[4] In 1977, the [U.S. Federal Communications Commission](/source/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,[1][5] although the specific rules have continued to evolve with changes to the [Emergency Alert System](/source/Emergency_Alert_System) and the introduction of [digital radio](/source/Digital_radio).[6]

## Theory of operation

An ATS monitors conditions such as [voltage](/source/Voltage), [current](/source/Current_(electricity)), and [temperature](/source/Temperature) within the transmitter cabinet or enclosure, and often has external [sensors](/source/Sensor) as well, particularly on the antenna. Some systems have remote monitoring points which report back to the main unit through [telemetry](/source/Telemetry) links.[7]

Advanced systems can monitor and often correct other problems which are considered [mission-critical](/source/Mission-critical), such as detecting ice on antenna elements or [radomes](/source/Radome) and turning on heaters to prevent the [VSWR](/source/VSWR) (power reflected from a mismatched antenna back into the transmitter) from going too high. High-power stations that use [desiccation](/source/Desiccation) [pumps](/source/Pump) to put dry [nitrogen](/source/Nitrogen) into their [feedline](/source/Feedline) (to displace moisture for increased [efficiency](/source/Electrical_efficiency)) can also monitor the [pressure](/source/Pressure). [Generators](/source/Electrical_generator), [batteries](/source/Battery_(electricity)), and incoming [electricity](/source/Electricity) can also be monitored.[7]

If anything goes wrong which the ATS cannot handle, it can send out calls for help, via [pager](/source/Pager), [telephone](/source/Telephone) [voice message](/source/Voice_message), or [dedicated telemetry links](/source/Transmitter/studio_link) back to a fixed point such as a broadcast [studio](/source/Studio). Other than possibly listening for [dead air](/source/Dead_air) from the [studio/transmitter link](/source/Studio/transmitter_link), an ATS does *not* cover the programming or the studio equipment like [broadcast automation](/source/Broadcast_automation), but rather only the "[transmitter plant](/source/Transmitter_plant)".[7]

An ATS can also be used to automate scheduled tasks, such as lowering an [AM radio](/source/AM_radio) station's transmission power at sundown and raising it at sunrise to meeting license requirements for different [propagation](/source/Radio_propagation) patterns at day and night.[1]

## References

1. Hallikainen, Harold (1996). ["Regulatory History of Operator Licenses and Transmitter Remote Control"](https://bh.hallikainen.org/uploads/harold/RegHistory.pdf). *The NAB Guide to Unattended Station Operation: How to Run Your Transmitter Without an Operator.*. Washington, D.C.: National Association of Broadcasters. ISBN 0-89324-247-0. [OCLC 41334048](https://www.worldcat.org/oclc/41334048)

1. Potts, Lyman & Norton, Robert (2003). ["Unattended Transmitter Operation — The Automon"](https://broadcasting-history.com/industry-government/unattended-transmitter-operation-automon). *History of Canadian Broadcasting*. Canadian Communications Foundation. Retrieved 2022-10-30.

1. Stine, Randy J. (2016-06-01 [2002-04-10]). ["From the Archives: NAB Honors 'Father of Automation'"](https://www.radioworld.com/miscellaneous/from-the-archives-nab-honors-father-of-automation). *[Radio World](/source/Radio_World)*

1. ["The Unattended Operation of U.H.F. Broadcasting Transmitters"](https://archive.org/details/bbc-monographs-85/page/n1/mode/2up). *BBC Engineering*. No. 85. January 1971. pp. 2–3. – via [Internet Archive](/source/Internet_Archive)

1. ["Unattended Operation of Radio and Television Stations"](https://www.fcc.gov/media/radio/unattended-operation). *Federal Communications Commission*. 2015-12-13. Retrieved 2022-10-30.

1. Stimson, Leslie (2007-07-04). ["FCC Looks at Changes to Rules Covering Unintended Operation"](https://worldradiohistory.com/Archive-All-BC-Engineering/Radio-World-Modern/2007/Radio-World-2007-07-04.pdf). *Radio World*. p. 3. – via World Radio History.

1. Hallikainen, Harold (2007). "Transmitter Remote Control and Monitoring Systems". *National Association of Broadcasters Engineering Handbook*. 10th ed. Burlington, Massachusetts: Focal Press. ISBN 978-0-240-80751-5. [OCLC 858995417](https://www.worldcat.org/oclc/858995417)

## See also

- [Broadcast automation](/source/Broadcast_automation) and [central casting](/source/Centralcasting)
- [Broadcast translators](/source/Broadcast_translator) and [repeaters](/source/Repeater)

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Adapted from the Wikipedia article [Automatic transmission system](https://en.wikipedia.org/wiki/Automatic_transmission_system) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Automatic_transmission_system?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.