rbn@brl-vgr@sri-unix.UUCP (09/14/83)
From: R. Bruce Natalie (CTAB) <rbn@brl-vgr>
----- Forwarded message # 1:
Received: From Cmu-Cs-C.ARPA by BRL-VGR via smtp; 7 Sep 83 10:14 EDT
Received: ID <DRT@CMU-CS-C.ARPA>; Wed 7 Sep 83 10:14:30-EDT
Date: Wed, 7 Sep 1983 10:14 EDT
From: DRT@CMU-CS-C.ARPA
To: rbn@BRL-VGR.ARPA
Subject: computers turning on when you call them.
Hello,
It seems the easiest way to do what you want is simply to connect
the carrier detect signal from your modem to a power relay on your
computer system. I hope you can use this idea. Any others I could
think of would be dreadfully expensive and hard to build.
Ross Thompson
DRT@CMU-CS-A
----- End of forwarded messagesdarrelj@sdcrdcf.UUCP (09/20/83)
An alternative power on trigger (for a computer which powers on when
telephoned) is the RingIndicator signal provided by many (but certainly not
all) modems on pin 22. This is a signal which is active whenever the modem
detects presence of ringing voltage on the phone line, so its a signal on
for about 2 or 3 seconds every 6 seconds or so. This signal should be
available whenever the modem has power (unlike carrier detect. Carrier
detect is presented only after the modem has answered the phone and
established the data connection, many modems will not do this unless DTR
(pin 20) is made true; if you have and use RI, the computer can control DTR
and decide whether to turn on DTR and permit the phone to be answered).
To implement this you will probably want three relays:
a 5 volt reed relay, normally open (this will be activated by RI or DCD to
turn on system
a 5 volt reed relay, normally closed (this will be activated by computer to
turn system off
a double-pole power relay, normally open (this will actually switch power
line).
The reed switches and the coil of the power relay should be in series
accross an appriate coil voltage (proably 12, 24 or 120 volts).
The coil of the NO reed relay should have one side connected to +5 volts,
the other side to the output of one section of an MC1489 RS232 receiver IC.
This IC needs +5v and ground for power.
The coil of the other reed relay should be hooked between +5volts and a
buffered output signal from your computer (e.g. the LED drivers for Apple
game paddles). If the port is an MOS port, buffer it thru a 7404.
Setting the output port to the right value will power off the computer.
(You might need an extra 7404 inverter section, since the state of the port
at initial power-on had better keep power on!
Darrel J. Van Buer, SDC, 2500 Colorado Ave, Santa Monica, CA 90406
uucp: {beats me}!sdcrdcf!darrelj
arpa: vanbuer@usc-ecl.milnet
tel:(213)820-4111 x5449