The book page returns as David Harwood takes a look at the latest offerings

As ZX moves into the monthly magazine market place, we on the book page are moving into the space age. Evidence of this are the books on offer ths month, dealing with hacking into the airwaves, Comets and modern network systems.

The Radio Hacker's Code Book, by George Sassoon, is for the person who has heard a little about Amateur Radio and wants to learn more about it.

Via the air waves messages are being sent from different countries all over the world (e.g. from TASS, the news agency in Russia, oil prices from the USA etc) and with the necessary equipment, these message can be downloaded into a home-computer. The initial section of the book describes the various RTTY (radio teletype transmissions) and the way they are configured. It explains that there are various encrypted messages and provides a description on how to decipher these garbled messages with your Spectrum. Various progams are included in Basic and Machine Code demonstrating how to achieve the results you require.

The book isn't an easy read as the amount of technical data is vast and covers everything the enthusiast would need to know when embarking on amateur radio. This is not a book that can be read over the cornflakes in the morning, but for anyone who wants to know about amateur radio and its uses for this is ideal. The price of £6.95 also is very reasonable and perhaps reflects the possibility that computer book prices are starting to come down. In the past, books of this technical nature have always been priced around £10.

The second book this month is called Comets and is written by David Burgess. This is one of a new range of books by The Computer Club, which aims to provide informative books to be used in conjunction with a computer.

The comet book uses BBC Basic for all its programs, but these can easily be adapted for the Sinclair range, and a section is provided at th end of the book to help the reader with this task. The book should teach the reader all about comets and enable you to carry out astronomy projects with a Spectrum or similar machine. Comets are introduced, with a brief description of their history (did you know, for instance, that Halley's Comet is depicted in the Bayeux Tapestry?) and an explanation on how the individual can try to spot his own comet.

There are a number of programs in the book, including testing the user's ability to see if he can actually spot a comet, a complete drawing of the solar system and (the book would not be complete without one) a games program to save the Earth from the falling comet bugs!

The book contains a lot of information on the comet and its composition, is very easy to read a bargain at £5.95 in hardback.

The final offering this month is in the same area as the other two and is called Hotline, by Ben Knox. Retailing at £6.95, the book explains how, when armed with a computer, the world of networking, bulletin board and electronic mail is at your fingertips.

The book is divided into two main sections and does assume the reader to have some basic computer knowledge. The first section explains how to go on-line and the second section shows what can be done once online.

In order to do this, the computer needs a modem, which is a device that connects the computer to the telephone line. A modem stands for modulator/demodulator and allows data to be received or transferred via a telephone line. Modems come in different types, with various options and features and the book adequately covers all of these, with a brief explanation of each. It would have been more informative though if the author went into greater detail about the baud rate or bps (speed) of the modems, explaining what the different speed rates meant, and the effect on the quality of the data at the higher speed rate and various error checking facilities.

I would like also to have another moan about the section on Auto Dial modems. This claims that, due to BT regulations, it is not possible for an auto-dial system to dial a number and, if engaged, repeat this until the line is free. This is not true. BT regulations allow a modem to repeatedly dial a number up to a maximum of five time in any four hours.

The books also claims that Hayes compatibility (an unofficial standard in the States) is not yet available over here. The Steebeck Dowly range *does* incorporate this Hayes standard.

After purchasing your modem software is then needed to allow your computer to communicate with the host computer via the telephone line. What you need to look out for when purchasing a software package is explained, but there are unfortunately no examples given of the best software packages. The remainder of the book discusses the various online systems available. Fortunately, the author does not expect you to pay up and sign on to all the databases available, but explains how to use the systems in demonstration mode. Prestel is the obvious first choice, but there is also a list of all the current bill boards available in the UK.

When using commercial and international systems, long distance calls are often required and can be fairly expensive. British Telecom, surprisingly enough, do provide the answer with something called the Packet Switch System (PSS). PSS is cheaper because it allows a number of callers to use the same telephone line at the same time; the technical term for this is multiplexing.

There is a PSS telephone number in most major cities and once dialled, the user enters his network user ID and the address of the host computer which he wishes to call. The PSS then does the rest for the cost of a local call and a small user charge to BT for the use of PSS. It stands to reason that the computer you are dialling needs to be a PSS subscriber as well. PSS is definitely a thing of the future and is well detailed in this book.

The remainder of the book explains Telecom Gold, with its electronic mail and telex facilities and also looks at Compuserve and Source, which are information retrieval systems in the United States, MUD, the Multi-User Dungeon game is dealt with, and the book explains how to log on and obtain a free demonstration of the system. Again, the author's research is lacking as the book states that PSS must be used to log onto the MUD. This is incorrect as it is possible to dial MUD direct.

The appendix of the book then covers various database services, gives a full specification of the RS232, although this is not really that useful, and a glossary of communication abbreviations and terms. All in all the book is very useful for anyone who wishes to know more about the communications age. In a few cases, the author gives incorrect details, which may be due to the book having been published in 1985, and if this is so, I do think that the book should have some sort of technical update for 1986.