Flashing Lamp Ring Indicators

[zaphod01]

This is probably the guy in Canada to whom I just sold several 95B dial blanks. He was asking the same questions. I told him to buy an ITT flasher phone to study the circuitry. I even sent  him a picture of one I just sold.

[dsk]

It is a few simple ways to do make that lamp.

Noway made their first transistorized rotary in 1967, a terrible sound:
Click on the grey telephone here: http://tinyurl.com/pktklls

Its nearly impossible to hear if its your or others telephone ringing in an office environment, so the Televerket decided to put on a lamp, and 2 versions were tested.
1 The neon lamp (aka indicators on an electric range) or
2 a glow lamp in the ringer circuit after the rectifier. 

The 2 seems to be the used solution.

I'll try to find a picture, its really ugly.

dsk

[twocvbloke]

There's the GPO's way of doing it too, as demonstrated in my 17A Handset:

http://www.youtube.com/watch?v=gUaowMnLUP4

Basically just a neon lamp (presumably 120v ish) wired in series with the ringer with a 15kOhm resistor paralleled with the lamp, the location in the handset is just for aesthetics, it could be located anywhere in a phone where it can be seen...

[AE_Collector]

John are you asking what made a lamp flash for Message Waiting, like on a hotel room phone? The neon lamp would flash with Ringing but could also b flashed on its own whe nbehind many different types of PABX's. The PABX could put a lower AC voltage onto the extension in a pattern similar to ringing that would not ring the bells but would activate the neon lamp to indicate a message waiting.

Terry

[Andre91]

The WE sets with a ring indicator lamp use a neon bulb. 120v neon indicator lamps are pretty widely available and would have the most authentic look, and be easier to wire into the phone. Plus they're designed for AC. If you wire it in parallel with the ringer, you'll likely need a resistor or two in series with it or ringer volume might be reduced, if the phone rings at all.

That makes sense but I seem to remember the light flashed during the ring so do you have any idea of what components were used to make the neon lamp flash at about 2 or 3 times a second, whatever the standard was? That was pre-transistor times so a 555 or other modern timing circuitry did not exist back then. Was it a simple thermal neon lamp that flashed on its own or something else?

BSP # 502-501-115 has a schematic of the flasher set, there is a schematic on page 22 of that document. Looks like a thermal neon connected across L1 and L2 with a 27k resistor in series with the lamp.

[TelePlay]

John are you asking what made a lamp flash for Message Waiting, like on a hotel room phone?

No, Terry, I realize a key or hotel type phone have lamps that are run by some sort of switching device in the background providing the light signaling. I am asking what circuitry would be inside a single line standard phone to flash a lamp when a call comes in. UK phones would flash a bit more just from the double short ring cadence there but in the US, the 2 second on 4 second off would not be a good flashing alert if one  just put a neon lamp on the L1/L2 lines. It would be too easy to miss the ring if the lamp were "off" for 4 seconds. A 555 timer circuit would require a lot including a rectifier, transformer and the 555 circuit to flash the lamp but that would only be during the 2 second ring cycle. I would think, for a ring indicator lamp to work well, it would have to flash continuously until the phone is picked up. I think that Radio Shack device plugged into a 120 VAC line would do just that until the phone is picked up. I just don't see how something like that can be installed inside a phone. The circuit would be large and complex and initiated by the first ring and then would continue flashing with the ambient DC piggy backed on the AC ring current. That make sense? If someone wants a ring indicator lamp, such as needed by the hearing impaired, it seems one of those external bright flashing devices would be best. To just drill a hole in a phone for a "show" lamp would be the waste of a shell. And if the ringer had to be turned off (silent mode) so just the lamp would be the indicator, that would mean another hole in the shell, is disconnecting the ringer. And then the 2 second on 4 second off cycle would mean many missed calls unless one stated at the light continuously 24/7  .

Just saying, seems not worth it to do it home made so better to go with the Radio Shack or equivalent lamp indicator if one really needs that function to know when the phone was ringing.

There are several currently for sale on eBay right now. This one is a bit higher in price at $19.99 plus Free Shipping but it is a BIN auction with 3 available, 2 already sold.

http://www.ebay.com/itm/121192074565

[AE_Collector]

The more modern Nortel phones that we used a lot of at work for Analog Centrex lines (9316 & 9417 {2 line}) all had wall warts to power the display, speakerphone, message waiting lite etc) so that took care of the problem. The message waiting lite flashed during ringing as well but I already have forgotten if it followed the ring cadence or began flashing on and off independant of the ring cycle.

Terry

[TelePlay]

The more modern Nortel phones that we used a lot of at work for Analog Centrex lines (9316 & 9417 {2 line}) all had wall warts to power the display, speakerphone, message waiting lite etc) so that took care of the problem.

Yes, most of those modern phones, and I have a few of them, included a wall adapter to put power into the phones for those functions. But for a 500? Don't know so I bit the bullet and bought one of those Radio Shack units (cheap too) on eBay. It has 3 screws on the back to get it open so when it arrives, I will be able to see what it does and how they do it. Stay tuned . . .

And, it will come in handy in the basement workshop where I run TV and/or radio quite loudly during working down there. Some of the restoration power tools do make a lot of noise . . .   and my hearing is no where what it used to be.

[Andre91]

We use the Radio Shack flashers in our radio control rooms, they certainly do the job. They are bright enough that they'll get your attention even if the unit is behind you. They do have a ringer in them as well, that can be turned off.

[G-Man]

Neither Issues 1 nor 4 not contain the content on page-22 that you describe.

Are you citing from another issue or page number?

When citing a specific page within a BSP it is often helpful to also include the issue number since the page content can vary from one edition to another.

Thanks

The WE sets with a ring indicator lamp use a neon bulb. 120v neon indicator lamps are pretty widely available and would have the most authentic look, and be easier to wire into the phone. Plus they're designed for AC. If you wire it in parallel with the ringer, you'll likely need a resistor or two in series with it or ringer volume might be reduced, if the phone rings at all.

That makes sense but I seem to remember the light flashed during the ring so do you have any idea of what components were used to make the neon lamp flash at about 2 or 3 times a second, whatever the standard was? That was pre-transistor times so a 555 or other modern timing circuitry did not exist back then. Was it a simple thermal neon lamp that flashed on its own or something else?

BSP # 502-501-115 has a schematic of the flasher set, there is a schematic on page 22 of that document. Looks like a thermal neon connected across L1 and L2 with a 27k resistor in series with the lamp.

[G-Man]

Message waiting lamps flash in response to the ringing current as each pole-piece within the neon lamp alternately flashes in relation to when the polarity changes during each cycle. Also, the presents of any dc biasing voltage may also affect the rate of flashing.

Also, it was the other way around since these sets were not introduced until a number of years later after the transistor was introduced by Bell Labs in 1948.

The WE sets with a ring indicator lamp use a neon bulb. 120v neon indicator lamps are pretty widely available and would have the most authentic look, and be easier to wire into the phone. Plus they're designed for AC. If you wire it in parallel with the ringer, you'll likely need a resistor or two in series with it or ringer volume might be reduced, if the phone rings at all.

That makes sense but I seem to remember the light flashed during the ring so do you have any idea of what components were used to make the neon lamp flash at about 2 or 3 times a second, whatever the standard was? That was pre-transistor times so a 555 or other modern timing circuitry did not exist back then. Was it a simple thermal neon lamp that flashed on its own or something else?

[Contempra]

Anyway, I don't buy this kind of phones because at each time I make a cleanup, nothing work...  ouff my poor English...

[G-Man]

Page 27 of 502-501-115, Issue 1 shows a standard message waiting set using an ordinary neon lamp connected in series with a standard 27K resistor. 

[TelePlay]

Page 27 of 502-501-115, Issue 1 shows a standard message waiting set using an ordinary neon lamp connected in series with a standard 27K resistor. 

Thanks. That's interesting and would be easy to bench test with a ring generator, a lamp and a resistor. Seems my memory was off in that the lamp only flashed while the ring voltage was present, 2 seconds. Thanks for providing the schematic. Very useful, indeed.

[Andre91]

Thanks-That's the page I was looking at.