Author Topic: Tube Lamp w/Side Lead-In & Contacts (Read 6640 times)

Chris Kocsis · « **on:** November 26, 2000, 12:52:00 am »

Here's an interesting lamp I just got. It's 1-5/8" long incl. the tip and 7/16" wide. The lead-in wires emerge on the sides and connect to two brass strips that are glued to the outside. Both of these strips have "4G" stamped into them. The lead-in wires look like platinum; the filament end seems to be flattened and punched with a hole, half of which is covered by the carbon paste or other glue. The hairpin filament is detached and stuck to the inside wall. On the outside rounded end it looks like there's residue of red paint.

Anyone seen one of these before? It looks like a switchboard or phone lamp in that it lodged between contacts in the socket.

[This message has been edited by Chris Kocsis (edited November 26, 2000).]

William Oelker · « **Reply #1 on:** November 26, 2000, 12:06:00 pm »

Hi Chris, I have seen this lamp many times. It was used as an indicator lamp in a Western Electric Telephone Key Set. It blinked on and off on an incoming call and blinked bright and dim on a (on Hold) call. And it stay lit when the line was in use. I am sure it was used in other indicator applications also. I believe the voltage for it was 48 VDC or 24 VDC. I am not sure what the voltage on this particular one is. They also had different current applications. Hope This helps. Bill

Chris Kocsis · « **Reply #2 on:** November 26, 2000, 11:22:00 pm »

Thanks, Bill! I thought it looked telephone-y. Those probably aren't platinum lead-in wires then, but they sure look like it.

Chris

James · « **Reply #3 on:** November 28, 2000, 06:30:00 pm »

Hi Chris,

The lead wires are probably nickel plated dumet which is why it looks like platinum. NPD is used for almost all modern miniature bulbs made on high speed machines because it withstands the higher manufacturing temperatures better than regular dumet wire. Flashlight bulbs nearly always use this wire.

In the UK there is a very similar bulb known as GPO2 (General Post Office Type 2) and the carbon filament variants of this were still being mass produced up to the early 1980's. They were killed off though with the advent of digital switchboards, however a limited range of tungsten filament equivalents is still in production today.

Hope this helps,
James.