Continue to Site

Welcome to

Welcome to our site! is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Looking for an analog electronics guru for help

Not open for further replies.


Junior Member level 1
Jul 31, 2002
Reaction score
Trophy points
Activity points
analog electronic guru

We use at work headsets for comunnicate from point to point, i.e. let's say we are about 5 miles apart, 2 wires between us, 2 headsets. The headsets have a Carbon microphone and a dynamic headphone, connected in series. now we attach a 6V battery in series and we can talk point to point. I cannot find this kind of microphones - about an inch in diameter - anywhere, and decided to construct a device that may replace them...I have no idea how to do that yet, as the charcoal mike change its resistance in function of speech (air pressure)...
The point is that I can find here only headsets with ELECTRET mikes...:(
I'll be very thankful if anyone could give me an idea or a place where I could find an idea...It's VERY important for me, my top priority project ....
Please HELP !!!

replacing carbon mic with electret schematic


i think the construction of your headset is similar the old "bell telefon" style.

In the past, 30 years and more ago, the carbon microphon was a part of all the telefon sets. I think you must search for old schematic and parts for old phones.


Right, I have those plans, but my problem is I have to change from carbon to electret type mikes, as i need to connect 3 persons to speak over 2 wires...I'm working at the telecom company, and workers have to use those devices for testing.

| |
>II earpiece II<
| |
IO Carbon Mike OI
| |
| |

this is the simple circuit. I MUST replace the carbon cartridge to an electret one. Changing to dynamic one is no problem, but I need an ELECTRET replacement....
Well, I see my drawing is not exactly piece of art....
Thanx :)

Hi mate, I work for a telecomms company that makes a lot of mics. We used to make those carbon mics, I remember those old knockerboxes to tap the carbon down, those were the days!

pm me, we can sort it out.

Not open for further replies.

Part and Inventory Search

Welcome to