Responding to an expanding hole in the market, modem manufacturer PMC Consumer Electronics has given its ISDN terminal adapter a make-over by adding fax and voice messaging capabilities to its specification. The result is the Pace ISDN Professional.

Virtually all dial-up modems are voice and fax-capable these days, but hardly any ISDN terminal adapters are. The explanation for this is that the traditional market for ISDN products has been businesses who are more than likely already catered for by a centralised voice messaging facility or fax machine. For businesses, an ISDN TA is there to do fairly specific tasks - to connect to another ISDN device for file transfers, for example, or to enable video conferencing or to connect to the Internet. Although ISDN is not as popular in UK homes as in other European countries, especially Germany, BT is now pushing its ISDN-compatible service, Highway. This is aimed squarely at home users and small businesses and both will tend to be attracted to a solution which includes voice and fax capabilities, like the Pace ISDN Pro.

PMC's hardware is fairly conventional. Connection to the host PC is, like an external modem, via a serial cable. There are two RJ11 analogue POTS (plain old telephone system) ports for connecting standard phones and phone devices and RJ11 to BT socket adapters are supplied. The usual array of status LEDs is clearly marked on the front panel of the compact black plastic case. Two-channel 128K bits/second aggregation is available if required and a fast 230K bits/sec serial rate is supported if you have a suitably fast serial port fitted to your PC. MNS (multiple number subscribing) is provided for configuring up to ten incoming phone numbers.

When we first read the specification of the Pace ISDN Pro, we were rather expecting PMC to have designed new electronics incorporating hardware support for voice and fax, just like their dial-up modems. In fact the ISDN Pro's hardware, though slightly updated, is largely the same as it's always been in earlier incarnations. The main difference is the addition of software emulation for voice and fax.

The supplied software, which comes from the German company, RVS, actually works very well - with voice recording quality superior to PMC's remarkable speaking modem, the Pace Solo. You can also use it to record conversations and even make calls without a telephone handset if you have a microphone connected to your PC's sound card, although you will need at least a Pentium 166 for the software emulator to operate optimally.

However, we were a bit crestfallen by the software route chosen by PMC. This restricts the usefulness of the ISDN Pro. Unlike the Pace Solo, the Pace ISDN Pro is not a stand-alone device - it can only receive faxes and voice messages when connected to a PC which is powered up and running the messaging software. If you used an ordinary, cheaper, ISDN TA with a fax machine and answering machine attached to one of the analogue phone ports, you'd have 24 hour service.

Compared to an Eicon Diva ISDN Modem we have been evaluating long term, the PMC ISDN Pro's built in features aren't as optimal as we have come to expect either. Unlike the Diva, the ISDN Pro can't ring both analogue phone ports together and allow either port to take the call. You either map the ISDN phone numbers of your line to each port, or a second incoming call gets routed to the second port if the first one is busy. This means you can't use the ISDN Pro as a simple 2-line switch.

As already mentioned, the voice and fax software is actually very good, although only a 'lite' version is supplied; you can upgrade to the full version, which allows remote access to messages, etc., for an additional fee. Slightly worrying, although not noticeable in practice, our Windows NT test machine did log several framing errors in the ISDN communications, something which never happened with the Diva box.