TBC

Timebase Corrector. This was often included as a part of a VTR to correct the timing inaccuracies of the pictures read from tape. Early models were limited by their dependence on analog storage devices, such as ultrasonic glass delay lines. This meant that VTRs, such as the original quadruplex machines, had to be mechanically highly accurate and stable to keep the replayed signal within the correction range (window) of the TBC; just a few microseconds.

The introduction of digital processing techniques made much larger stores, with analogue inputs and outputs, economic, so widening the correction window and reducing the need for especially accurate, expensive mechanical engineering. Digital TBC has had a profound effect on VTR design – and price. Quantel’s first product was a digital TBC for use with IVC VTRs.

When VTRs went digital (DVTR) the TBC function became easier and was always a part of the DVTR. With the wide use of disk or solid-state video stores the TBC function has disappeared as data is accurately timed by buffers and clocks built into the equipment.