Typically used in the telecommunications industry up to the early 1980's
If you were a technician in the telecommunications industry (especially exchange or subscriber PABX switchboard based) many, many years ago then you would know these lamps 'intimately', although long-life, these were constantly in need of being changed on switchboards in particular.
I have included a photograph of a pretty typical switchboard of the day, with those lovely weighted cords (automatically retracting using hanging weights inside the switchboard) and rows of jack sockets with the small lamps directly above each jack. These lamps indicated incoming calls or in-use (busy) if an incoming call was patched to an extension. This type of switchboard was also used in the telephone exchanges for inter-exchange communications (I remember checking trunk circuits between exchanges using one of these - using single tones (not DTMF) backwards and forwards for signalling, all under the control of the tech sitting at a switchboard similar to these. Later equipment releases for exchange use went to DTMF for signalling across trunk circuits but did not use the standard DTMF tone frequencies ... so many memories! Not to be confused with the "Test Desk" switchboards (for local and telecommunications system wide testing) which had a large meter sitting vertically in the middle of the desk for line testing (voltage, resistance and leakage of the circuits under test). These were special in that they had direct access to the 'final selectors' in the SXS exchange and ANY subscriber line was directly accessible from the switchboard, for testing and monitoring. Remember the days when someone, during a telephone conversation would suddenly say "Hey Joan ... did you just hear that click?" Often it may have been someone at the Test Desk "dropping" onto the line, mostly for legitimate reasons but sometimes .... hmmm
These days I believe these lamps would only be of interest for restoration of historical telecommunications equipment.
I have a separate advertisement some dual switch/lamp assemblies, these lamps do fit those assemblies.
TELECOMMUNICATIONS INCANDESCENT WEDGE LAMP
No. 2 G.P.O
Part #725
17V operation
Tungsten filament
Wedge style (these were inserted and removed with a little tool similar to very small pliers but with half cups at the end, to grip the lamp glass envelope)
I am fine with supplying even just one lamp, there are no minimum quantities set but if you purchase a few more, an automatic discount is applied
