Their output had an aspect ratio of 5:4 and was cropped for transmission to 4:3. It first appeared at 7 p.m. on Monday 18 February. The digital standard used is that specified by the EBU for a digital parallel interface. While the device has only analogue outputs, to suit present installations, the EBU specification defines the required sampling rates and levels for luminance and chrominance. A further advantage is that the Quantel Paintbox handles data in a form quite close, but not identical, to this format. To produce the overall effect two full frame-stores are used. One is the foreground store which holds the highlighted gold shell, and the other is the background store for the shaded blue disc and the captions. These stores hold only a single frame, and there is no restriction on their content. They are full colour and can display any picture produced by the Quantel Paintbox. These stores are generally known as the 'fixed' memory. The memory structure is similar to that used for the recently introduced digital Test Card F generator, but each card can hold more data, and can be a part of a larger data-base. The EPROMs used are 27128 16 kbyte devices, although the memory card can take 27256 and even 27512 devices as, and when, they become available. When fully populated with 27128s each card holds 0.5 Mbytes. The EPROMs in question contain 20 000 pixels of map data pre-rendered as frames of animation. Each card has on its side a yellow LED that lights up when that card is in use. The controller unit has a 24-bit sequence address bus giving access to 16 Mbytes, but the equipment has space for only 7.5 Mbytes, and is fitted for 5 Mbytes. The controller also addresses the fixed memory through a 19-bit address bus. This memory uses identical cards to the sequence memory and four are in parallel. A result of this is that the customising for each region affects only the data on two cards in the system. In fact, since only the caption is different for each, only 16 EPROMs are specialised. The controller also decodes the sequence data from its highly compressed format into a usable 13.5 MHz data stream, and distributes timing information to the rest of the system. Timing control is useful, since it can eliminate the need for external synchronising. This equipment's output can be