[Asterisk-Users] door phone

[Matt White]

Jon Pounder wrote:
> I posted my solution yesterday and it is $50 so not sure why people are
> still asking for a cheap solution.
> 
> I have a cheap disposable "walmart" phone on the channel bank, in
> immediate mode so when it is picked up it jumps immediately to the default
> context.
> 
> I can also dial it like any other extension to talk to people at the door.
> 
> I have a $20 electric strike on the door which is coupled to my burglar
> alarm (that I can use a keypad outside to open right now) to interface to
> asterisk all I need is the following about $5 worth of stuff.
> 
> 10k resistor from one of the data lines on the parallel port to base of a
> 2n2222 transistor, emitter of 2222 to ground/earth, collector to a coil of
> a 12vdc pcb mount relay, 1n400x diode in inverse parallel with the coil to
> kill spikes, other end of the diode/coil to 12vdc from a disk drive
> connector in the pc. normally open contacts of the coil in parallel with
> whatever else drives the door strike (normally a 12-24AC/DC supply - AC if
> you like that Buzz, DC if a click is more your liking.)

Just as another data point, you could look at something like

http://www.x10.com/products/x10_um506.htm

It's an X10 module (powerline control system) that provides basically an
on/off switch for low-voltage devices (up to 5A at 24VDC).  Pretty much all
you need then is the power supply and the strike.  The main advantage is
that being an X10 device, you don't have to run wires all the way to
your computer room.  All you need is your X10 computer interface (like
the "FireCracker PC Interface (CM17A)", which every good geek has
already, right?  :-)

-- 
Matt White                          whitem at arts.usask.ca
Arts and Science Computer Labs      University of Saskatchewan

It sure is Monday... Ain't it a sin
I've gotta work my way thru the week again.
	- Mark Chesnutt..."Sure Is Monday"