The Penman Plotter is flexible, accurate and draws pretty pictures. Even better, it is good value, says Kenn Garroch

The Penman Plotter is probably one of the most unlikely looking gadgets I've ever seen. It's a fully function, intelligent plotter than can cope with up to A3 size paper. At the moment, it is only available for the BBC, Apple and IBM but, as it works through an RS232 channel, it can be connected to any machine with this interface. Costing about £250, it is a high quality product that could well take off.

The Penman is packed in one of those boxes that is made to be carried away. With it come three sets of pens (the Hewlett-Packard type), some demonstration software, an RS232 cable, a power supply, some paper, and a set of three adaptors for other types of pens.

The plotter itself has a rather fascinating design. At first sight, it appears to be a large plastic box (33.5cm x 12.5cm x 5cm) with very few distinguishing features, apart from the RS232 and power sockets.

Closer examination reveals that this houses the turtle-like plotter, the cable, and all the fancy electronics that control the system. The plotter head sits snugly inside the case which, when removed, has a trailing ribbon cable attached to it. This is used to send commands to control the motors and pen lifting mechanism.

The underside of the remote unit reveals a little more about the workings of this strange beast. There are two small motor-driven rubber wheels and a trailing bogie, in a triangle. Two light sensors on either side sense such things as the edge of the paper. Using the triangular base, the outline of any shape can be constructed by moving it around; a similar idea to using two pins and a piece of string to draw an ellipse.

For demonstration purposes, the Penman has a built-in set of routines that allow it to strut its stuff, without having to connect it to a computer.

After admiring the demonstrations, it was obvious that the time had come to hook the Penman to a computer. The review model came with software for the BBC Micro and connection is simply a matter of plugging the cable into the RS232 socket on the plotter, and the RS423 on the BBC.

Auto booting the disk gives an introductory screen and revealed one of the other uses for the Penman. It can be driven around as a mouse. The current position/vector is fed back to the computer and used to position a cursor on the screen. The only drawback in using it in this mode is that it doesn't feel like a mouse, as you can't move it in all directions without twisting it. Apart from this, selecting the menu options is easy. There are a number of demonstrations options with the supplied software, from simple plots to a program that pages in Acornsoft Logo and runs a program in it. The latter is quite neat as it allows anything that would normally go on the scren from Logo to be plotted out on paper i.e. the Penman becomes a real-time turtle.

Another part of the demo program outlines a whole list of predefined procedures that allow the plotter to be programmed from Basic. The details for these are not terribly explicit but at least the manufacturers have tried to allow for simple programming.

Using these procedures is quite easy, simply load in the program that contains them, knock off the first the lines or so, and renumber from line 1000. All that then needs to be done is to write a program that includes the routines.

One niggle here is that it is rather difficult to work out which procedures use other procedures so, once the program is finished, the unused ones can be removed to save space.

The accuracy is claimed to be 0.1mm in cartesian mode and .035mm in polar mode. The latter looks very good when drawing curves but a change of direction in cartesian mode can cause small errors to creep in.

Plotting is usually started with the plotter in the home position - the top left-hand area of the paper. If drawing takes a lot of movement, it is generally a good idea to go home fairly often, otherwise the accuracy gets progressively worse.

One thing that shows the intelligence of the machine is when it appears to get wrapped up in its cable, it works out how far round it has gone and spins the other way until it is unwrapped.

The plotting is always very definite and its three colours produce a plotting quality that is only surpassed by more expensive plotters. Commands are sent down the RS232 and stored in a buffer - similar to using one of those ballpoint pen printer/plotters, although the commands are not the same.

Programming it directly is not to be recommended, as the commands are pretty complex. It needs a start command, the command itself, and an end command. Using the predefined Basic procedures is a lot easier and less time-consuming, unless you want to install it on another machine.

I was very impressed with the Penman Plotter. Its price and flexibility, plus the fact that it can cope with up to A3 paper put it a cut above the competition. If you need good quality plotting at a reasonable price, the Penman is without doubt a good buy.

Features	5/5
Documentation	3/5
Performance	4/5
Overall Value	4/5