Back-lit switches: Difference between revisions

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Back-lit switches (view source)

Revision as of 06:30, 5 December 2016

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There is one miniature 5 V incandescent lamp per interlocking group of buttons, with clear plastic light guides reflecting the light to the backs of the transparent plastic buttons.  In the Off state, a small metal flap covers the un-lit button end, in the On state it is pushed open.
There is one miniature 5 V incandescent lamp per interlocking group of buttons, with clear plastic light guides reflecting the light to the backs of the transparent plastic buttons.  In the Off state, a small metal flap covers the un-lit button end, in the On state it is pushed open.


The lamps are not supplied from the standard +5 V (logic supply) rail but from a separate lamp supply rail which is not present in all mainframes (e.g. missing from most 76x3 series scopes).  In mainframes that do supply the lamps, the lamp voltage (and therefore lamp intensity) can often be varied, e.g. through a 3-way (off/mid/high) switch in the back of the instrument.  In the [[7904]] (non-A), this is a front panel control.
The lamps are not supplied from the standard +5 V (logic supply) rail but from a separate lamp supply rail which is not present in all mainframes (e.g. missing from 7xx3 series scopes - see [[Media:040-0686-01.pdf | modification 040-0686-01 adding this supply]]).  In mainframes that do supply the lamps, the lamp voltage (and therefore lamp intensity) can often be varied, e.g. through a 3-way (off/mid/high) switch in the back of the instrument.  In the [[7904]] (non-A), this is a front panel control.




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