One of our advertisers is missing. Indeed another of the Sinclair family of product sellers has gone.
Some will have noticed that the advertisement for T&C Services was not in the last issue of QZX. That business has disappeared into the woodwork. The telephone number which has graced the pages for more issues than I care to count is being answered by people who have not heard to that long time QZX advertiser. This particular business will be missed because their advertisement is the longest running advertisement for Sinclair products in the world. Their support for QZX has been an important factor in keeping the publication alive and is much appreciated.
But while one goes another comes, this time with a rare but essential part. Nazir A. Pashtoon under the name of NAP_WARE is selling all Timex or QL programmable array logic chips. These are IC chips which look lke easily available chips but are not. For details of the contents of the ZX81 PAL, as they are called, see previous issues of QZX. For details on the new business (located near Chicago) call (708) 439-1679 in the evenings.
The Capital Area Timex/Sinclair Users Group (CATS) has recently obtained some very useful file compression programs for the QL. They have been added to the disks in their hbrary. Three programs, ZOO, HAR, and LHX are available. These are archiving programs, much like the well known PKZIP used in the MSDOS world. These three programs are used on a variety of systems. All three allow you to pack a number of files into a single compressed file or to just compress a large file.
File compression is great for uploading a large file or a number of files as one file to a BBS or for a packet exchange. they also compress QSL programs and logs to save disk space.
All the programs come with source code to make it convenient for those who want to study the file compression algorithm or tinker with the programs.
The group also has a copy of QLUNZIP, a program for the QL which will unzip files that have been archived using PKZIP. This is a popular program used on packet to reduce the transmission time and to lessen the chance that a collision will slow the transfer.
You can contact Tim Swenson, Box 11017, Takoma Park, MD 20913 for information on how to join CATS or otherwise get access to their library.
QZX must be doing something right. Almost 40% of a recent newsletter received here was made up of reprints from QZX. (Of course, part of that issue of QZX was made up of reprints too.)
The main article this month tells how to add an interface to the ZX81. This interface can be used for such things as controlling beam antennas, switching equipment on or off. at selected times, activating packet equipment, or controlling automatic battery chargers. It is best to use buffer circuits on the output of the ZX81 as does this equipment because the unbuffered outputs have very little drive capabilities. This is a particularly good building project because it uses a Sinclair computer for a task for which another computer is too large and expensive. Furthermore the limited monitor and keyboard capabilities of the ZX81 are not important factors for I/O controllers.