A circuit that outputs 3V when there was a pulse

[Mr. Man-wai Chang]

Is there a simple circuit that does that?

[Jon Danniken]

How long does the 3V need to last? What should happen if there is another pulse during the desired "3V on" duration?

Jon

[Mr. Man-wai Chang]

I want to flash a super-bright LED when there is an incoming phone call. Talking about the good, old fixed-line telephone.

[gfretwell]

Pretty easy to do with chips. Get a ring detector chip and an SCR. Connect the ring detect to the gate of the SCR and reset it by opening the circuit to the LED on the SCR anode.

[Retired]

You mean to make something like this:

[trader_4]

A quick google produced this, which is cheap and should serve the purpose:

That's first thing I saw, probably more on Ebay, etc.

[Mr. Man-wai Chang]

Could you name one chip?

[Mike Duffy]

How bright do you need? They did this 50 years ago with a neon bulb.

No extra diodes, resistors, etc. are required. I assume that the voltage & current are still within the same tolerances.

[gfretwell]

I thought he wanted the LED to latch on to show a missed call. If you just want to light a LED when the bell is ringing I would put a couple hundred volt silicon diode (1n4003 or similar) in series with a

6.8k or so resistor and the LED. That should get you close to a typical 15ma through the LED. Lower ohm resistor will get you a brighter LED ... until you blow it. Check the spec if you want to be pedantic about it. Dr Ohm will give you guidance based on 100v or so ring voltage.

[Mr. Man-wai Chang]

I found that neon bulb inside the handset of the fixed-line telephone. I wanna make it flash brighter, so I want to replace with a modern LED.

SO how could I replace this neon bulb with a modern LED?

[trader_4]

You;ve been given several suggestions now, from a cheap ring detector module that has a relay output that you can buy, to putting a diode and resistor with LED on the phone line. And you didn't initially say where this has to fit, exactly what you're trying to do. It's still far from clear. Now it sounds like you want to replace an existing neon bulb in an old phone, where that bulb is probably driven directly by the ring voltage? In that case, Gfre's solution of a diode and resistor with LED sounds like it could work.

[Mr. Man-wai Chang]

Thanks! Will look into that and do my homework first.