When a home smoke detector is operating does it emit an electronic signal of some sort? If there is such a signal is the frequency known, does it interfere with anything? Is it noticeable, are people sensitive to it?

I am not sure I understand your question. By operating do you mean that it has detected some or fire? If that is your question then the answer is yes. If you are talking about while it is just hanging on the wall and no smoke or fire is detected it does not make a noise, with one exception, if the battery is low it will beep every few seconds to alarm you about the battery.
It is possible that you are wondering if it is putting of some kind of signal maybe like radiation. It that is what you are asking, I doubt that it does but I am not sure.

I was asking about when in detection mode. Just hanging on the ceiling. No not radiation, just EMI type stuff.
What I am trying to figure out is why my landlord won't put batteries in the smoke detectors. I live in an old house that has been converted to 4 apartments. There are smoke detectors in the units, and in the common areas. Installed where they should be. But none are working because they have no batteries in them. I'm trying to determine what might make a landlord take such an incredible risk. I'm sure he's violating the fire code here in Rhode Island. If there is an injury or worse, he'll go to jail, and loose his property. Is he just an unbelievable lame ***? Or is there some other motivation going on? Do people say smoke detectors cause cancer, or make an imperceptible hum, or do they interfere with electronic equipment, spy cameras or bugs? I don't know, and I'm trying to get any facts before I confront him about it.

There is no reason not to put batteries in a smoke detector other than utter lack of responsibility.

You can contact your local codes inspector to inspect the building and most likely the landlord will get cited. Where I live (my father-in-law is a codes inspector) it is required that all detectors have batteries.

You may be able to contact your local fire department to get the facts without reporting to the codes inspector. However, if calling the inspector you need only to ask questions and not give addresses. Similar to what you did here.

The answer to your question, (surprisingly to me!) is YES. The two most common types of smoke detectors DO emit things (one uses light, one uses radiation).

Read all about them here: http://home.howstuffworks.com/smoke.htm

However, this is NOT A GOOD REASON to disable them! Your landlord, if this is his reasoning, is definitely lame in the brain. Most likely (because of cost), your smoke detectors are photovoltaic. They put out tiny bits of light. This is harmless. Even IF they are the ionization type, you'd have to break one open and stand in front of it for a thousand years to suffer any ill effects!

I'm exhaggerating, but you get the point. The fire codes should be followed, and the detectors should have batteries.

But hey, I learned something in looking this up! I would have bet money they were totally passive.

Cheers,

James

One of the problems with battery operated smoke detectors is that when the battery is low, they emit this chirp that drives people nuts. You tend to only hear this chirp at night when everything else is quiet and you can't sleep.

If you have multiple battery operated smoke detectors, the landlord is probably sick of getting calls in the middle of the night to replace batteries!

They do generate a signal, Counter would determine frequency.
Good example of generated signals on something unsuspecting would be TV Remote control. Turn radio on and to low end of AM band, press button on remote, You will Hear the pulses.(Remote need to be close to radio or antenna)This was quick check before
They came up with card which allowed viewing of IR.