Electronics Forum / Electrical Engineering / April 2007

Have the standard NID (network interface device) telephone box on the
outside of my house.
But, there is also a smaller J 104 labeled box right next to it.
Did a lot of Googling, but cannot find anything on a J 104, or J104, box.

I've got a piece of lab test equipment that's about 30 years old. The cooling
fan is very loud and I'm looking for ways to quiet it down.
I measure the fan's noise at 53dB (using A-weighted dB meter at 1m on-axis),
although the fan mfr only rates it at 39dB. I attribute the ...

What is about the smallest size (in terms of physical dimensions) that a
transformer could be made suitable to step 7200 volts down to 240 volts
in utility grade service, including any cooling parts as might be needed?
Assume a very small load is all that needs to be powered, such ...

A coating machine in a print shop utilizes a 1-meter-wide, 10-foot-long
conveyer. The belt for this part of the machine is 1cm (approx) mesh of what
appears to be carbon fiber. Drive is via 200mm rollers at either end of the
conveyer section.

If you have a series circuit with two resistors on that
circuit, and your power supply is a 6 volt battery, then
given that both resistors are 1 ohm, you would end up
with 3 amps. This means that across each resistor,

Convinced that here in humid Taiwan, detaching the battery for the six
days of the week that I don't use my UPS will prevent corrosion of
certain internal UPS parts, I detach one of the battery terminals.
(Also perhaps I also thus eliminate some very minor drain on the (pair

Here's a question. Say I have a transformer and instead of wiring the
primary and secondary in series (like all the textbooks do) I want to
wire them in parallel. What total inductance would I measure for the
two windings both with adding and subtracting mutual coupling?

Hi, everyone.
Can anyone point me in the direction of the specifications for Subject
instrument.  I've just refurbished one that I rescued from the
dumpster, but I'm not sure over what frequency range it works - checks

I have a question about temperature coefficients.
I'm using an LM340 (5 volt regulator) and don't understand how much heat it
will disapate and how much it will change over temp.
The datasheet specs 0.8mV/c but doesn't show a junction to case spec.

If you are interested in training that gives you 'real world'
experience, have a look at the website http://www.testandcert.com
Here you will find lots of information about courses etc. that will
give you experience and confidence in domestic testing and

I've read conflicting definitions for voltage drop.
Some sources describe it as 'voltage lost'
while others 'voltage difference'. I tend to favor
the latter. My reasoning is as follows: If voltage

What happens at the atomic level
where electrons have an affinity for
a path of least resistance? Imagine this,
you have a parallel circuit. And at the node

I have a problem where my AFCI breaker (Siemans Type OAF 15amp) trips
in my bedroom.  It has done this sporadically over the past 3 years
since the house was built.  Sometimes it will clear itself up and
sometimes it will not.  I most recently replaced the AFCI breaker and

Some posters to se* post multiple messages (one to each n.g.) rather than
cross-post. Is this just ignorance of proper procedure, or is GG's web
interface not capable of x-posting?
I'd look for myself, but I abhor GG and get hives when I go near it.

I have a 10.5kW shower running on 240V.
10mm sq Twin&Earth cable run of 20m running through various materials
Board protected by an RCD.
I want to protect this circuit via an MCB (I have a MEMERA 2000 Board