Dr. Dobb's Journal September 1999
Credit-card-sized, single-board computers combined with global positioning satellite (GPS) systems are revolutionizing electronic tracking devices. Land, Air, Sea Systems (http://www.landairsea.com/), for instance, has introduced a device that lets observers sitting at a desktop or laptop computer monitor in real time the location and speed of a target vehicle -- your teenager's car, a white Bronco, the trucks in your shipping company fleet, or a suspected criminal's car being tracked by law enforcement officials.
The tracking device, called "Mobile-Trac," attaches to the vehicle and is powered by a single-board 80486 computer manufactured by ZF Microsystems (http:// www.zfmicro.com/). A low-priced version ($1295.00) of the system, about the size of a VHS cassette (including battery pack and magnetic attachment), stores the vehicle's travel history on a PCMCIA memory card. The top-of-the line version, called "Mobile Watch," is priced at $2995.00. It uses a cellular modem to transmit the travel data in real time to a host computer. In both cases, information is displayed on a digital street map, with the vehicle's progress marked by a colored line. A time history of the vehicle's speed and geographic coordinates is also displayed.
But tracking systems can also be used for less intrusive purposes. As its name suggests, Land, Air, Sea Systems also produces devices for tracking aircraft and boats. ZF Microsystems's single-board PC is also used in a GPS-based system for aerial fertilization of cropland. ZF Microsystems provides an SDK for developing products based on its OEMmodule 486 single-board PC.
-- Nick Baran
Students at the University of Delaware have put out to pasture thumb thumping, skin scratching, stem sniffing, and other age-old tests for determining whether or not a watermelon is ready to eat. How? By developing a computer-controlled ripeness sensor that attaches to a watermelon on one end, and a laptop computer on the other. A prototype version of the UD watermelon ripeness sensor -- developed by Matt Behr, Dave Bartoski, Allan Cohen, and Jason Firko, as part of a senior design class -- spits out a ripeness reading in about 12 seconds.
A small mallet attached to a metal arm protrudes from one side of the sensor, while a microphone sits close to the melon on the other. When the mallet strikes the melon, the microphone picks up the sound and transfers it via electric signal to the computer. The voltage signal is then converted into digital information, which is analyzed. The melon's thunk produces an acoustical signal that shows up as a peak on the computer screen, which dies down gradually. Melon frequencies range from 100 to 250 hertz, corresponding to the desired sugar content of 8 to 12 percent. The sensor was designed not for end users in the grocery store, but for farmers and distributors who grow more than 1.5 trillion pounds of watermelon per year.
-- Jonathan Erickson
The developers of the Apache web server have announced the formation of the Apache Software Foundation (http:// www.apache.org/). The nonprofit foundation will serve as the umbrella organization for the Apache web server and related open-source projects. Chaired by Roy T. Fielding, one of the founders of the project and author of the HTTP/1.1 protocol, the Apache Software Foundation will provide organizational, legal, and financial support for related collaborative development projects.
The finalization of the paperwork was something of a coup for the Apache project. Unlike other projects that have created similar umbrella organizations, such as the BSD variants (FreeBSD, NetBSD, and OpenBSD), the Apache group did not have a single person leading the technical and organizational direction of the project; operating instead in a completely democratic fashion. Because of this and the inconvenience of creating the organization, especially for people primarily interested in software development, the process took two years.
Nevertheless, the step was a significant one in guaranteeing the future viability of the Apache project. Already one of the leaders in convincing large corporate entities such as IBM and Sun to contribute code, the existence of the Foundation should make it more compelling for companies to contribute to the project, in addition to providing an infrastructure for legally protecting its developers, distributing money, and organizing other projects, such as the Apache Developer's Conference.
-- Eugene Eric Kim
The Internet Engineering Task Force (IETF) recently released the HTTP/1.1 Digest Authentication Standard as part of RFC 2617. HTTP/1.1
Digest Authentication is designed to enable secure communication and logins between web browsers and servers by preventing unethical users from masquerading as legitimate users by copying passwords. The previous standard, HTTP Basic Authentication, sent the password over the network unprotected. Digest Authentication improves on the Basic scheme by verifying the identity of both parties connected. Users are identified to the server and, at the same time, the server to users to ensure that each party is who he claims to be. Basic authentication only provides one-way verification of the user. This standard has been integrated into the Digest login scheme in Microsoft's Internet Explorer 5.
-- Jonathan Erickson
Xerox and 3M are teaming up to manufacture a reusable electronic display referred to as "electronic paper." Developed at Xerox PARC by researcher Nick Sheridon, electronic paper, which is almost as flexible as ordinary paper, is based on a technology called "gyricon." A gyricon sheet is a thin layer of transparent plastic in which millions of small beads are randomly dispersed. The beads, each contained in an oil-filled cavity, rotate within those cavities. The beads are bichromal, with hemispheres of contrasting color (black and white), and charged so they exhibit an electrical dipole. When a voltage is applied to the surface of the sheet, the beads rotate to present one colored side or the other to the viewer. A pattern of voltages can be applied to the surface in a bit-wise fashion to create images such as text and pictures. The image will persist until new voltage patterns are applied to create new images.
-- Jonathan Erickson