atcomsystems.ca/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems Can anyone tell me why...

Matt, there is also a subject that we have not broached yet...

Station Busy lamps !!!

These are lamps, either free-standing indicators or spare lamps in a tel set, that light when a particular station goes off-hook. The station in question can be a SLT or a key set. A pick up key need not be pressed to activate the lamp. Just the fact that the phone is ROH is sufficient.

The scheme uses the A ground circuit, as it passes through the SWHK contacts of the victim's phone. The A ground in the phone is protected against a sneak path by putting a blocking diode in series with the SWHK and the Hold key A ground lead. Then, an additional A ground goes out from the SWHK through a lead in the mounting cord (usually the Y/Br lead), and is then cross-connected to a lamp which has -24 DC waiting on its other side.

The application for this is generally a secretary who needs to know when a boss's phone is ROH.

ITT used to make a box that would mount on the wall of an office, that had rear-lit numbered discs, one for each honcho in the office. The receptionist could then determine which boss (for instance partners in a law firm) could take the next call.

Cool!

I telecommute, so I'm the boss. Now.... where to get a secretary....

But wouldn't -24v blow the lamp? Also, whats ROH? I'm guessing <something> off hook?

As for the lighted discs.... damn. When I was a kid the refurbed the local bowling alley, including putting in new pin indicator lamps (the boards at the end of the lane that tell ya which pins are still standing). I took one home; would have been perfect for this. I could of mounted it in the living room to tell which station was off hook.

Oh yeah - I also took home one of the score desks - the deal with the overhead score projector. I wanted to also take home a ball return, but the overhead was as far as mom & pop would go.

PS:

Saw this on ebay, might it be related to what you are talking about? It was listed as a western electric device.

Matt,
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But wouldn't -24v blow the lamp? Also, whats ROH? I'm guessing <something> off hook?
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Yes, if the bulb isn't a 24v bulb. ROH = Receiver off hook.


Scrounged part of a bowling alley lane once to build a workbech. HEAVY! For anyone interested the alleys were/are made of maple strips about 3 inches wide, 1/2 inch thick, and 3-5 feet long, ON EDGE. All measurements approximate, this was 30 years ago. Glued and nailed. Destroyed two saw blades cutting the width down to 30" X 8 feet. By the way, as I recall, it took 8 of us to load the original slab of alley in my van and the van sagged! That was Lucky Strike Lanes, about 87th and Wornall Road, Matt. John C.

Ah yes, Lucky Strike...! I always hated to see that place go... one of the coolest neon signs I've ever seen. Come to think of it, most of Waldo was neon (I grew up in that area). The bowling alley we scrounged was @ red bridge. And the CO dumpster dives took place over at Red Bridge/Holmes.

I think you once told me you were from KC - but I didn't realize how close....!

Arthur -

What a memory! I'd completely forgotten about them. I don't think I've installed one in 35 years.

Matt -

BLFs were a stock item in the early '70s. We'd wire a diode into the set and feed the BLF on the receptionist's desk (or wall). The unit could be ordered either -24VDC or 10VAC and it came with a variety of transparent label overlays (depending on which system you might want to use it with) Usually we matched the numbers to the ICM. On a K-10 where the only spare was the Y/O pair we'd use 1 wire for a buzzer and 1 for a blf with a common ground for both.

Sam


Yes that unit which was available in 1,2,3,or 4 lamp models was a standard (small) BLF.

You could only use DC, not AC, for the lamp, because the blocking diode would pass half of any AC on the busy lamp lead, causing the A relay in the line circuit to chatter.

That's why the original BSP called for switching the lamps from 10 volt ones to 24 volt ones, as the most prevalent source of DC was -24 from a typical key system supply.

But, of course, there were resourceful I/R people who quickly figured out how to derive -10 Vdc and then the field hassle of carrying 24 Volt lamps down in the bottom of the tool box was solved.

The 10Vdc was manufactured by putting a full-wave rectifier on the output of a Trimline transformer, (output 6-8 Vac nominal) and grounding the positive side through a forward-biased BMF diode to drop the voltage another 0.7 Volt. On average, it gave slightly more than 10Vdc, but the lamps survived due mainly to the voltage drop across the many feet of 24G IWC through which the lamps were powered.

Arthur, is 'BMF diode' an official description, or a slang expression that described the diode in.. shall we say,.. unsuitable for mixed company language. John C.

Arthur -

As I recall, we used to take a spare switchook lead and feed a ground through it and over to the BLF. We may have used two diodes - one facing the BLF one facing back the other way to prevent backfeed. The BLF lamps sat on 10VAC and were switched on with the ground.

I really can't remember exactly. I hate this getting old stuff. I means it's been more then 30 years - but still! I'm going to have to look at the prints and see if anything jumps out at me,

Sam

BMF = a slang description of which the first word is Big.

Sorry to resurrect a dead horse, but my SLT's are now being fed before the line cards.

Bad A/A1 punchdown was the culprit, as I think someone mentioned way, way, way back.