This article originally appeared in TidBITS on 1994-05-09 at 12:00 p.m.
The permanent URL for this article is:
Include images: Off

PowerSwitch LT: Controlling Power Via LocalTalk

by Kee Nethery

My home LaserWriter is tucked away in a closet corner where it's difficult to turn on and off, especially when I'm on a different floor. I don't like leaving it on for long periods of time because the lights dim when it power cycles (it's a power hog) and I've seen the repair bills for office LaserWriters left on year round. My solution is the PowerSwitch LT from Radiant Enterprises.

The PowerSwitch LT is an intelligent power outlet with an ADB port for controlling a Mac directly and a LocalTalk port for attaching to a LocalTalk network. If you want to control a device remotely, the PowerSwitch LT can probably handle it. It can power up your office Macintosh when you dial in through an Apple Remote Access server, automatically reboot LocalTalk routers when they freeze, control power to appliances, and - my favorite - power on a LaserWriter (or any LocalTalk-based laser printer) when I print and then turn it off after a period of inactivity. If half of the Apple LaserWriters ever sold are currently kept on round the clock, and if each had a PowerSwitch LT, the energy saved could power all the homes in Rochester, New York or St. Petersburg, Florida.

Before the PowerSwitch existed, if you wanted to access your computer remotely through an Apple Remote Access server (Cayman, Shiva, and so on), you had to leave your Mac running constantly. By attaching a PowerSwitch, you can turn the Macintosh off when you leave the office and on those occasions when you need access to it via ARA, communicate with the PowerSwitch, enter your password, power on the peripherals, wait a couple of seconds, then power on your Macintosh with an ADB command. The PowerSwitch comes with software that enables you to issue a Shut Down command to reverse the process.

When networking hardware devices (routers, modems, etc.) must be rebooted, they are always physically far away and everyone at the remote site has gone home (it's just one of those rules). The PowerSwitch can be paired with a remote device such as a router, server, or ARA server so that it watches for packets coming from that device. If the device stops sending packets on the network for a configured amount of time, the PowerSwitch automatically powers it off, waits a number of seconds, then powers it back on. This is extremely useful if you manage devices in far away locations.

As I said, my favorite is power control of a LaserWriter. When the LaserWriter is off, the PowerSwitch pretends to be the LaserWriter. Pull down the Chooser and you see all the LaserWriters, even if they all are powered off. When you print, the PowerSwitch powers on the LaserWriter, PrintMonitor tells you there is a problem printing, you tell it that you would like to try printing again, and it prints on that second try. My LaserWriter is set to power off if I don't use it again within thirty minutes. For offices, an extension on the receptionist's Macintosh can keep the LaserWriters on while that Macintosh is on, thereby skipping the PrintMonitor message and still powering it off at night. [The PrintMonitor complaint that it can't find the printer is the most irritating part of using the PowerSwitch. I'd like to see Radiant fool Print Monitor into not complaining, or at least provide an FKEY to turn it on beforehand. -Tonya]

A flashing push button on the PowerSwitch indicates that it is functioning and enables you to physically switch power on or off without using software. The button sticks up, so I put my PowerSwitch on the floor - when I step on it, my LaserWriter powers on.

Installation is relatively simple, just plug the device you are controlling into the PowerSwitch 15 amp power outlet, plug the PowerSwitch into a power outlet and attach a network connector. If you use the PowerSwitch to control a Macintosh, connect the PowerSwitch to the Macintosh with an ADB extension cable. Radiant makes an ADB Y-splitter cable for Macs with only one ADB port.

You configure the PowerSwitch through a rather clumsy HyperCard stack that is explained by a mediocre and confusing manual. The PowerSwitch can be manually controlled from the Chooser and can pretend to be any Choose-type device, such as a LaserWriter, NetModem, Coffee Pot, Photocopier, or Macintosh. Any software that can execute HyperCard XCMDs can be used to control a PowerSwitch. Offices that have several LaserWriters can have them all turn on in the morning by using an extension that powers them on when a Mac is on.

The configuration is password-protected and on/off control can also be password-protected. The password uses a random number exchange so that the actual password does not travel across the network. Passwords make controlling routers realistic, since you wouldn't want someone to accidentally or maliciously power off your routers. To make passwords easier to manage, PowerSwitch offers a text field where you can leave a note about the location of the password or who has the password. Since the note is in the PowerSwitch, anyone on the network can read it.

All the latest Radiant software (including their Analog/Digital I/O software, and video camera pan & tilt control for QuickTime) is available on America Online in Radiant's area (keyword = radiant).

The PowerSwitch LT is sold directly by Radiant for $199. Last but not least, I used to work at Radiant, and I helped design the PowerSwitch hardware so I am a bit biased. [Which is why we've tested the PowerSwitch for a while, and can vouch for its everyday efficacy. -Tonya]

Radiant Enterprises -- 415/395-9940 -- 415/395-9646 (fax)