Broadcast Automation - Early Analog Systems

Early Analog Systems

Early automation systems were electromechanical systems which used relays. Later systems were "computerized" only to the point of maintaining a schedule, and were limited to radio rather than TV. Music would be stored on reel-to-reel audio tape. Subaudible tones on the tape marked the end of each song. The computer would simply rotate among the tape players until the computer's internal clock matched that of a scheduled event. When a scheduled event would be encountered, the computer would finish the currently-playing song and then execute the scheduled block of events. These events were usually advertisements, but could also include the station's top-of-hour station identification, news, or a bumper promoting the station or its other shows. At the end of the block, the rotation among tapes resumed.

Advertisements, jingles, and the top-of-hour station identification required by law were often on "carts". Short for cartridges, these were endless tapes similar to 8-track tapes, and looked nearly identical as well. A primary difference between carts and 8 track deals with the pinch roller and capstan. The roller was self-contained in an 8-track; carts had a slot for a pinch roller on a spindle which was activated by solenoid upon pressing the start button on the cart machine. This allowed for nearly instantaneous playback start without artifacts. Mechanical carousels would rotate the carts in and out of multiple tape players as dictated by the computer. Time announcements were provided by a pair of dedicated cart players, with the even minutes stored on one and the odd minutes on the other. This meant an announcement would always be ready to play, even if the minute was changing when the announcement was triggered. The system did require attention throughout the day to change reels as they ran out and reload carts. It became obsolete when a method was developed to automatically rewind and re-cue the reel tapes when they ran out, extending 'walk-away' time indefinitely.

Radio station WIRX may have been one of the world's first completely automated radio stations, built and designed by Brian Jeffrey Brown in 1963 when Brown was only 10 years old. The station broadcast in a classical format, called "More Good Music (MGM)" and featured five minute bottom of the hour news feeds from the Mutual Broadcasting System. The heart of the automation was a 8 x 24 telephone stepping relay which controlled two reel-to-reel tape decks, one twelve inch Ampex machine providing the main program audio and a second RCA seven inch machine providing "fill" music. The tapes played by these machines were originally produced in the MWF's Madison, Wisconsin production facility by WSJM Chief Engineer Richard E. McLemore (and later in-house at WSJM) with sub-audible tones used to signal the end of a song. The stepping relay was programmed by slide switches in the front of the two relay racks which housed the equipment. The news feeds were triggered by a microswitch which was attached to a Western Union clock and tripped by the minute hand of the clock. and then reset the stepping relay. Originally, 30-minute station identification was accomplished by a simulcast switch in the control booth for sister station WSJM (AM), whereupon the disc jockey in the booth would announce "This is WSJM-AM and... (then pressing the momentary contact button) ...WSJM-FM, St. Joseph, Michigan." This only lasted about six months, however, and a standard tape cartridge player was wired in to announce the station identification and triggered by the Western Union clock.

A different technology appeared in 1980 with the analog recorders made by Solidyne, which used a computer-controlled tape positioning system. Four GMS 204 units were controlled from a 6809 microprocessor, with the program stored in a solid-state plug-in memory module. This system has a limited programming time of about eight hours.

Satellite programming often used audible dual-tone multi-frequency (DTMF) signals to trigger events at affiliate stations. This allowed the automatic local insertion of ads and station IDs. Because there are 12 (or 16) tone pairs, and typically four tones were sent in rapid succession (less than one second), more events could be triggered than by sub-audible tones (usually 25 Hz and 35 Hz).