Pilottone

Pilottone (or Pilotone) and the related neo-pilotone are special synchronization signals recorded by analog audio recorders designed for use in motion picture production, to keep sound and film recorded on separate media (otherwise known as double system recording) synchronised. Before the adoption of timecode by the motion picture industry, pilotone sync was used in almost all 1/4-inch magnetic double system motion picture sound recording from the late 50s until the late 1980s. Previous to the introduction of 1/4-inch audio tape recordings were made on 35mm optical cameras and then later, with the introduction of magnetic recording, 16mm or 35mm magnetic stock. The first 1/4-inch recorder capable of recording a synch track to regulate the playback speed of the recording was made by Rangertone and was a variation on the soon to come pilotone system.

History
According to Carsten Diercks, camera operator and filmmaker at West-German Nordwestdeutscher Rundfunk (NWDR) during the 1950s, pilottone was invented at the NWDR studio in Hamburg-Lokstedt, West Germany by NWDR technical engineer Adalbert Lohmann and his assistant Udo Stepputat in the early 1950s for single-camera 16mm TV news gathering and documentaries. The first program featuring the use of pilottone was the documentary Musuri - Es geht aufwärts am Kongo ("Musuri: Upstream/progress at the Congo"), shot in early 1954 in Africa and first broadcast on ARD on March 31, 1954. The new technology required new editing suites, and Musuri camera operator Diercks turned to a small nearby 6-man workshop named Steenbeck. The subsequent success of priorly shunned 16mm for TV program gathering facilitated by the pilotone system turned Steenbeck into a multinational corporation.

Neo-pilottone was invented in 1957 by Stefan Kudelski with the Nagra III tape recorder.

The new technology of pilottone was brought to international attention by its use by Richard Leacock, former cameraman of filmmaker Robert Flaherty, in his documentary feature Primary (1960), documenting the competing Democratic presidential nominee candidates Hubert Humphrey and John F. Kennedy. Diercks himself helped the spread of pilottone in the USA when he was the only Western reporter allowed to shoot in Havana during the Bay of Pigs Invasion in April 1961. CBS secured the licensing rights to Diercks's material via Norddeutscher Rundfunk (NWDR had split in 1956 into NDR and WDR), and brought it on air on May 14, 1961, ten days prior to the German broadcast of the same material. At a time when North-American TV program gathering was dominated by either Movietone (see also Movietone News) or magnetic pre-striping for live-sound recording, and the use of pilottone was still unheard of, according to Diercks the US TV networks were impressed with the system demonstrated by the 60-minute documentary feature.

Technology
The synchronisation was obtained in one of two ways. The original system used a microphone cable connected from the motion picture camera to an audio recorder such as those made by Stellavox or Nagra. A camera with a Sync motor sends a 60/50 Hz signal to the recorder, which is recorded as a sine wave pilot tone. This system was eventually replaced by a crystal in the audio recorder which generated the 60Hz signal and a crystal controlled camera motor.

The audio recorder has two recording heads, a full track mono head that records audio in the standard configuration. The second record head is the neo-pilot head (this head also doubles for playback of the pilotone signal). This head is orientated 90-degrees off of the audio head and is recorded down the middle of the mono audio signal. This signal being 90-degrees out of phase (and being a push-pull signal) cancels itself out and is inaudible on the audio playback head (similar to when a single audio signal is split to two channels and the phase on one is flipped, when the two tracks are played back at equal levels the signal cancels itself out). The only drawback to this system is that when a pilotone tape was played back on a stereo recorder the 60-Hz signal could be heard (unless the two stereo channels were combined back to mono).

On playback, the pilot head becomes a push-pull playback head in order to reproduce the pilot tone. The player compares the reproduced pilot signal to the 60/50Hz) line frequency, (which drives the synchronous 16/35mm mag recorder motor) and corrects the playback speed accordingly. Newer 16/35mm recorders used an internal quartz oscillator and the 1/4-inch tape player references the played back pilot signal to its own highly accurate internal crystal oscillator.

Normal audio tape recorders have good regulation of tape speed, but not sufficiently precise to guarantee that a playback machine will exactly match the speed of the recorder over long periods of time. Pilottone provides such a system.

Obsolescence
The pilottone system was phased out in the early 1990s when SMPTE timecode became the synch reference standard. The advantage of timecode over pilotone synch is that it is not only a speed reference but also a positioning reference. The hour:minute:second:frame readout that timecode provides allows the film transferred to tape or digital, or video precise matching of picture and sound.

The only "problem" with timecode is that it is a machine read system so picture and sound must be transferred to an editing system (such as DaVinci Resolve or Adobe Premiere) to be synched and edited. With the use of editing programs becoming the standard in film industry, this is not seen as a huge issue, however for some movies by e.g. Quentin Tarentino, that are still shot on analog film, this can cause some trouble.