scope:

Introductory Discussion

Within the control of entertainment lighting and effects time synchronization is very important. In a typical system this can require that hundreds or thousands of individual and autonomous components are required to behave in a coordinated manner to achieve a desired effect, and the coordination needs to remain the same night after night.

The variation in synchronization must therefore be imperceptible or at least unobtrusive to an audience.

Historically, connection between a controller and a piece of controlled equipment has taken the form of a direct linkage by wire and in most cases a single controller has been the main or only source of commands. In this model, synchronization is down to the performance of the controller and to the well known characteristics of the wire connection. Delays within the system of tens of milliseconds can easily be compensated if they are nearly constant - and are anyway often imperceptible when the object of control is an incandescent lamp with a filament time constant which ranges into hundreds of milliseconds.

With control of an ever widening array of equipment controlled in entertainment technology and the inclusion of equipment with very short time constants such as LED based or video effects, much smaller time discrepancies become perceptible - especially when sound, lighting and other effects are combined.

Within an ACN system the linking factor for control of all these components is the network - they cannot be relied upon to have any other linkage. However, delays and variation within the network infrastructure can mean that there is much more variability - even where total delays are no greater - than with the historical model described above.