Extracts from Ideas and Realisation in Lighting Control by Fred Bentham, Tabs, Sept.1966.
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 All routing and indicator switching now takes place on a small printed circuit card which forms an integral part of the plug-in luminous dimmer unit. These photographs show the difference in size between the new unit and the relay bar it replaces. Not only this, but as all this takes place on the back of the dimmer lever, wiring is reduced to simple busbarring and cabling across the dimmer lever sockets. The large relay banks (above) and the enormous jig-made cable forms all vanish. Furthermore, there is no need for a specialist to trace out faulty contacts. Should any channel play up, then the lever is just extracted from the front and a new one plugged in. This is of little weight so replacement by post is obvious. |
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Enough about circuitry. What does the system do? What facilities does it give the operator? This is how any stage lighting control has to be judged; the electronics are only incidental. |
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On System LP the dimmer scale itself is translucent and carries two internal indicator lamps, one red and one white. In addition, the scale can be depressed against a spring to use it as a push button for routing purposes (photo left). The levers mount at 5/8" centres horizontally and 4¼" vertically. All confusion between one lever and another is avoided by the special cutaway shape of the dimmer knob which not only provides ample space for the finger to rest but places it over the scale to which it refers. |
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The recommended form (photo left) has three presets, each of which is mounted as a horizontal row over the other. This allows easy operation within a preset and also facilitates matching when necessary of intensities from one preset to another. Other than the three preset levers per channel, there are only the master controls, no separate grouping push buttons, switches or indicator lamps being necessary. Indication and selection is at the dimmer levers themselves with consequent reduction both in space required and in uncertainty in observation. |
Master controls are kept as simple as possible and are concerned with grouping on to the two master faders (the white and the red) per preset. To do this there are five master push buttons to each preset - All White, Individual White, All Black, Individual Black and Individual Red. The Individual White and Individual Red pushes are used to set up groups on the White and Red faders. Any dimmer scales touched while either push is being held will be routed to the appropriate fader and light up in White or in Red. In addition, dimmer channels can be selected as common to both faders and display both red and white. Thus a preset can in effect be formed into three groups and a cross-fade be carried out with some channels, for example the sky, remaining static, without resort to another preset. Channels are removed from a master fader by using the "Individual Black push" in the same way.
The "All-White" or "All Black" pushes operate without the need to select individually at the dimmer scales. This can be very useful when simple non-group presetting is required since at a touch all channels can be set on the white. These "All" pushes are also helpful when setting either nearly full or almost empty combinations. Thus, if a lot of channels are concerned, they can all be set "on" at one touch and those not required then removed using "Individual Black" and/or "Red". In the same way using "All Black" the preset can be immediately cleared to "off" and the few required picked out in white or red or both as appropriate.
It is important to realise that the groups formed on System LP are quite independent on each preset. In this it differs from the push button system S.P. Thus six independent groups or blocks of light, or nine if the commons are included, can be set at any one time. It is not difficult to imagine raising first this block of light and then that. All the lanterns of the groups are still under individual control for balance and change if necessary.
In other control systems this practice of separate grouping to each preset as already stated entails extra work in matching groups when cross-fading group by group from preset to preset, but on System LP such matching, when required, is quite automatic. All that is needed is to press either of the two amber matching pushes associated with each preset master. These can either couple down the group of another preset as an addition, or if "All Black" is pressed first, as a substitute.
The red lamps need not necessarily be used together as the master group they may form, but can act as "markers" to identify a series of scattered dimmers to be brought in sequentially one after the other by hand. Likewise, in a part of a show depending on several switching changes in rapid succession one or two of the presets can be used for setting these in advance merely to be copied onto the active preset when required. Since the inactive preset masters would be kept off, such use of the touch contact facilities would not prevent the actual dimmer levers on these presets from being already set at a series of levels ready for later use.
The
compact nature of the dimmer lever and its integral routing card makes possible
self-contained desks for forty to eighty channels as already shown above. The
width of the latter being 57" overall. However, for this, and certainly for
larger ones of one hundred or more channels, the ergonomic wing unit and a separate
small centre desk will be preferable. The photo right shows what this would look
like in a room at the back of a theatre auditorium. It will be clear how conveniently
close to hand everything is. A single-sided wing leaves space for auxiliary controls
or other equipment on the operator's other hand as in the photograph, where a
switch patch panel and remote colour filter change controls are in fact accommodated.
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