Hands-free always-on intercom


I generally hate when people start asking questions before they’ve
done enough research, but because my situation is, um, challenging,
I’m hoping some of you will have mercy on me and help spoon feed me
a little.

My wife suffers from a degenerative neurological disorder. It’s
guaranteed to only get worse with time. Besides the physical handicap,
she’s showing signs of dementia as well. Our house isn’t grand, but
it’s big enough and has enough corners and doors and whatnot, it’s
often difficult for us to hear one another between rooms. Further,
if she fell or something under just the wrong set of circumstances
(me in the shop with equipment running, for instance), I wouldn’t be
able to hear her call for help, no matter how loudly she called.

The main reason I’m writing here is that sometimes she gets confused
and it is really hard to do anything else when I have to keep running
back and forth to answer her questions. Also there is a safety aspect
here that I really can’t ignore. What I’d like to do is set up an
always-on home intercom. We can’t use something which requires her to
walk to a unit on the wall and push a button or whatever to contact me.
Both mentally and physically that won’t work, and it really won’t
help if she breaks a leg in a fall. Even a wearable fob wouldn’t work.
Dementia, remember? She needs to be able to just call out no matter
where she is, no matter what doors are open or closed, and I need to be
able to hear her well enough that I know what’s on her mind and be able
to respond to her. I can think of about a dozen places where I’d like
to put a microphone and a speaker. Many of them quite near each other,
yes, but again, I don’t want to have to worry about a door being closed
or something blocking her voice should she have a real emergency.

Yeah, I thought about baby monitors, but a) we both really want
something wired (would you want every conversation you have with your
spouse broadcast to the neighborhood?), and b) I’d have to buy about a
dozen pairs, they’d all have to work together, and since they’re really
not designed for that, I’d imagine feedback would be a real issue.
I could see that costing a lot of money and in the end, not working.
I looked into commercially available intercoms, but they are a bit
spendy, but more importantly, I couldn’t find one that works quite
how I’d like it to (I guess there isn’t a big market for the whole
always-on, hands free, any unit to all other units intercom thing).

To try to get what I’d really like, I’m thinking of using a couple
SheevaPlugs (en.wikipedia.org/wiki/SheevaPlug) or similar
networked together, each with a bunch of the cheapest USB audio
cards I can find (that’ll still do the job, of course) to handle
several microphone/speaker pairs on each system (again, the cheapest
microphones and speakers I can find that’ll still do the job).
I’m thinking with a setup like that, and with Asterisk running on the
plugs, I should be able to treat each of those USB audio cards as a
phone, make them all automatically dial in to a conference call at
system startup time, and we’d have a hands-free always-on whole house
(including shop and garage) intercom system.

If you don’t know and don’t feel like following that link, SheevaPlugs
are just fanless (also diskless and headless) fairly cheap little
computers that I can hide away just about anywhere. They have an
SD card slot, one USB port and gigabit Ethernet, and that’s about it
for expansion and I/O. I’d probably be putting Debian on them just
because that’s what I’m most familiar with.


Does anyone know of a reason why that won’t work?

Does anyone have a better idea?

Can anyone tell me what I need to be sure to look for in a USB audio
card? I know NOTHING about sound cards in general, and even less than
that about the USB ones. It’s just not something I ever got into.

Does anyone have any specific recommendations for any particular
hardware (audio card, microphone, speaker) that’s a particularly
good value?

I’m concerned about feedback. Is Asterisk able to keep nearby speakers
from feeding into nearby microphones, even ones that aren’t on the same
audio card?

Is there a way to set a minimum volume threshold on the microphones?
I’d like to make it so you have to raise your voice a little so
various shufflings and mumblings we all make as we go about our day
don’t get transmitted, and as long as the TV is set down low, it
doesn’t get transmitted either. Certainly NOBODY wants bathroom
noises broadcast over an intercom.

What about noise cancellation? It’s not an absolute requirement, but
boy it sure would be nice to not have to mute the mic in the shop, and
just let the system filter out the noise from machines as I turn them
on and off out there. I can make do with a manual mute button, but
it would be really nice if I didn’t have to. Can Asterisk do that?

Speaking of shop noise, is Asterisk able to automatically turn up
the volume of a speaker when it detects the associated microphone
is picking up a lot of noise? That would be a really nice touch.

One more thing: I’d love to be able to take something out in the
yard with me so we can still communicate when she’s inside and I
have to be outside. I’m thinking of something like one of those
microphones that are worn on the ear like public speakers often use,
except two-way, not just a microphone. Something that’s always on and
leaves my hands free so I can work. The microphones are easy enough
to find, but I haven’t been able to find anything that has a speaker
as well as a microphone. Something that has a wire running down to
a unit that clips on my belt would be fine with me. It must have
enough range that can I stray from the house, and of course needs
to tie into the rest of the system. I’d have to be able to turn
off the base unit when not in use, but I doubt that’ll be a problem.
Does anyone know where I might find such a thing? Does anyone even
have some keywords that I might Google?

Again, I’m really sorry about asking all these questions without
doing more research on my own. I’m hoping for mercy. I am a bit of a
hacker, but the whole telephony, sound card, microphone, speaker thing
is outside my expertise, and the time I have to spend on this project
is pretty limited. I have two friends who are familiar with Asterisk
who have volunteered to help get me up to speed with it, and help me
with some of the configuration stuff, so I’m hoping some of you folks
might be willing and able to help with some of the rest. Those of you
who have taken care of a handicapped spouse will understand that it
can take a lot of time and energy, so the less of both I can expend
on this project the better. I’m hoping once it’s done, it will save
me some time and energy in taking care of her, as well as help me help
her in an emergency.

Thank you all,

Firstly, as well as push the button triggers, you can also get special social alarm triggers that are designed to automatically detect a fall, and will alarm without any action from the victim.

Secondly, I think you are over-designing. If you use Asterisk at all, you want only one instance, that runs a conferencing application. For everything else, I would strongly advise using built for the purpose IP phones. They are likely to have better echo cancellation, etc.

Using Asterisk itself as a softphone is a bad idea. At the very very least use a dedicated softphone application.

David, thank you for your reply.

Well, the ones I’ve heard of are something that’s worn. She’s not going to wear a gizmo. I did mention the dementia, didn’t I? Well, if I didn’t, I am now. That wouldn’t fly. Besides, this system isn’t just for falls, it’s primarily to save me from having to constantly run back and forth to answer the same question over and over.

Well, I hadn’t really designed anything at that level yet, but OK. One machine would be the master, and there will probably be one or more satellites. I figured these things would make themselves evident as the process unfolded.

Well, I looked into IP phones a bit, but there were a few things I didn’t like about going that way: 1) It seemed like it was going to be pretty spendy. If there are cheap ones out there, I didn’t find them. 2) I would have to have a bunch of ugly office phones everywhere. I thought I should be able to hide a mic and speaker more easily. 3) I didn’t think I’d be able to set up an IP phone to automatically dial itself in whenever it’s plugged in. I’d much rather have a system that would just come up by itself after a power outage than have to run around the house dialing all those phones in to the conference.

OK, can you suggest some softphone applications that you think are good? That would be very helpful.


[quote=“tg01”]David, thank you for your reply.

Well, the ones I’ve heard of are something that’s worn. She’s not going to wear a gizmo. I did mention the dementia, didn’t I? Well, if I didn’t, I am now. That wouldn’t fly. Besides, this system isn’t just for falls, it’s primarily to save me from having to constantly run back and forth to answer the same question over and over.[/quote]

I can accept that one couldn’t rely on a button getting pressed in moderate to severe dementia, but I don’t think it is inevitable that a dementia sufferer wouldn’t be prepared to wear a trigger. In fact, I believe there are wander alarms that rely on the sufferer wearing RFID devices and people use GSM trackers.

Unfortunately, in my direct experience, it was the caring partner that wasn’t prepared to wear a trigger, even though she was at risk of falls herself. As such, encouraging the sufferer would have been difficult, because they would have been aware that they were being singled out.

OK, I don’t want to go into details of a number of reasons, but I know my wife. She won’t want to wear a gizmo. The beginning stages of the dimentia will only make it harder to convince her.

It doesn’t matter why, really. The main thing is that this doesn’t solve the problem I’m trying to solve: I really need to be able to talk with her no matter where the two of us are in the house, no matter which doors are opened or closed. There can’t be any push to talk involved, and we can’t rely on any form of gizmo wearing (and certainly not carrying one, or $10 walkie-talkies would be fine). The fact that I also want to use it as a safety thing is really mostly secondary. If she falls or something, there are only a few circumstances under which I wouldn’t immediately hear, and it wouldn’t be a very long time before those circumstances change, and then I would be able to hear her, so I’m just not as concerned about that. I just want her to have the comfort of being able to just talk to me whenever she’s uneasy about something, and yet still allow me to get things done as I’ll be able to talk to her without having to keep going back and forth.

Do you have any recommendations for me for a softphone? Are there some that can deal with having multiple audio devices connected to the same computer more gracefully than others? In particular, do you know of some that can be run completely from the command line? I’ll need that so as to make everything come up automatically at startup. Do you have any recommendations for any of the various bits of hardware I’m going to need like USB audio, microphones, speakers, etc? Can you give me any pointers on things I should look for in these various bits of hardware? Can you give me pointers on how to deal with things like echo, feedback, noise cancelation, auto-volume and the like? On the other hand, you recommended putting IP phones everywhere. Can you recommend some models that aren’t terribly expensive, and preferably won’t make it look like I’ve gone crazy buying phones to put all over the house?

Please folks: Any help with any of the above would be very much appreciated. This is a huge task for me because I know so very little about any of these things, and I suspect some of you could save me a huge amount of time and money with just a few words. Just telling me what to look for would be helpful.