As far as I remember, SSL fitted 36v/20 Milli amp T5.5 bulbs in ALL their Highland switch bulbs to begin with in the late 1970’s apart from the 681 keyboard panel which was fitted with 24 volt bulbs (defaulting to Studer tape machines which were the norm then).
More on that later as SSL adjusted the DL41 and 42 track remote wiring to make the lamps light up ONLY when the tape machine went into record, rather than when the record button was actually pressed (it then needed a tally back from the tape machine to CONFIRM the tape machine was actually going into record rather than just the lamp lighting up on the console regardless).
The smaller 682 (rather than the 681) tape remote panel could have had several tape remotes on it (82E17 cards to switches) and the lamps depended on the tape machines involved when SSL got the original spec from the client.
From memory, the 681 and 682 panels had different lamps fitted as follows when SSL knew what the tape machines actually were. I remember changing various bulbs on these two panels many times to suit the tape machines used.
Studer tape machines had 24 volt lamps
Otari had 5v or 12v lamps (I can't remember)?
Some others had 12v lamps?
As someone else mentioned, the lamps on the 681 and 682 panels were powered by the tape machines via the S28E and S29E cables.
Hope this helps and clarifies things a bit. I worked at SSL from 1980 until 1987.
Jim Lassen
