MOREX has produced a Centronics and a proper RS232 interface for the Spectrum. Both are contained in a small black box which plugs into the back of the Spectrum. Only 850 bytes of machine code are required to operate the interface and it is located below the USR-definable graphics section of the 16K or 48K RAM - both versions are supplied on the same tape.
Both interfaces will operate via the LLISIT and LPRINT commands once a call to the machine code has been made via the USR command. The RS232 will also allow INKEY$ from an RS232 device. The code sent can either be all codes from 0 to 255 or they can be sent as TEXT which would normally appear on the screen.
Various speeds can be set on the RS232 to a maximum of 600 baud on a 16K machine - it can be set higher but the manual warns it can be unreliable - or 4,800 baud on the 48K. The baud rate cannot be split, to work Prestel for instance, at 1,200 one way and 75 the other.
The RS232 has the same handshaking as most professional devices - CTS, RTS and TX, RX data - on a 7-pin DIN socket. No plug is supplied.
The only difficulty was finding some device with which to try it. It will not work with non-standard devices as it requires a negative voltage to register as the LOW condition. With a BBC Micro Model B it worked very well; as the BBC allows the RS232 to act as the keyboard, the whole machine could be controlled from the Spectrum, which should be very useful for schools.
The RS232 is also a both-way device, so PRINT statements and programs can be fed into the Spectrum as well. It is simple to use and very well-documented in the manual supplied, including a list of system variables for machine code users.
The Centronics interface has a 26-way IDC connector - the same type as the BBC - so there should be no difficulty in obtaining a printer cable. A graphics tape is also included for Seikosha, NEC or Epson printers to permit a screen COPY to be done in two sizes - but not using the COPY command.
The edge connector is also extended through to the back for any other add-ons and the port addresses used are 254 and 127.
The Morex interface costs £45.95 from Morex Peripherals ltd. An RS232 lead to a 25 D-plug costs £13.45. It will also work with a version of Tasword-2, the Spectrum word processor.