Electronics Forum / Basics / September 2007

Hi, I have to build a telephone handset amplifier
which has to amplify both the speaker on the ear
(incoming sound) and the mic (outgoing voice).
It has to be powered by 3xAA/AAA batteries

I used to collect Popular Electronics which is no longer published.
What magazines are available now? Which ones would you recommend?
Thanks.

hi i wanna know a good antivirus n spyware,,tht may be super.

Is there a source of information you can recommend that deals with the more escoteric
aspects of component selection?
I know what a transistor is and what it does but is there a recommended purpose for metalic
vs carbon film type?

Anyone have any simple circuits on how to make +/- 12VDC from 0-24VDC?
I would just take a center-tapped transformer, but the idea is to use
a cheap off-the-shelf power brick like the ones you can grab from
Goodwill (thrift store) for $1 each.  No center taps there...

I'm considering the idea of compensating a BJT current source (or
sink) for temperature variation.  I haven't read any detailed web
pages, mostly because google doesn't find much with:
  "temperature compensation" "bjt current source"

I'm testing rechargeable batteries and would like a voltage-controlled
resistance so I can easily adjust the load with a program.
I'd appreciate recommendations on how to design this.
Thanks,

I'm a French guy so my english is limited...
I've designed and build an audio analyseur.
see
http://cjoint.com/?jnuQ3MN7sa

Is this capacitor bipolar or polarized?
http://www.avxcorp.com/docs/Catalogs/tps.pdf
Thanks!

I have two questions:
1. If you touch lead solder, does it get on your hands?
2. If the answer to question 1 is yes, if you touch a textbook, etc.,
does the lead on your hands go on the book?

Prop 65 max limit for lead is 200 ppm.
I wonder if there is any good testing kit that can detect lead on
surface around 200 ppm?
Any good recommendation? Thanks

Is it possible to modify an MP3 player (I have one of those
stick-shaped mp3 players to play with) so it plays a music track
continiously?
Or (probably better) possible to get the player to switch on and start

I think i have found the residue of alkaline battery leakage onto a
malfunctioning circuit board  ?
could this cause problems ? what is best way to clean a circuit board ?
denatured alchohol ?

I had one of those bug zapper things that looks like a mini tennis
racket only with a wire mesh. It ran on a 9v battery and was
exceptionally effective. :) Sadly I made the mistake of taking it to
Australia where it got spotted by customs and confiscated. :(

I'm trying to record cassettes and LPs to my PC and am experiencing
line noise, possibly from some other device in the house. I have not
determined the source of this noise, but it occurs at random times
during the day, and causes clicks and pops that ruin any recordings. I