specified in the Gemini CPU card manual. Connecting the computer to the modem
is then dead simple; all you then need is a cable with a male plug at one end
and a female socket at the other with each pin connected to its corresponding
number, ie, 2- 2; 3- 334- 455 – 53 6—- 6; 7 – 7; 8 – 8; 20 – 20.
Now comes the dodgy bit:
4) Connecting To BT
Connecting to BT is something of a grey area. Presumably if you buy a brand
spanking new modem, ie, spend more that £100 and it is BT approved with a BT
jack plug, you can plug it straight in and off you go. Surplus modems, even
ex-Telecom, are, however, a different ball game since:
4. When becoming surplus they probably lose immediate BT approval.
ii They generally do not have a correct jack plug on them when you buy them.
As far as I understand the current regulations, you are supposed to call
BT up to put a correct plug on your modem to work with your existing
Technically, if you do not comply with the above you can be prosecuted by
BT for using illegal equipment especially if when you wire it up, you
make a mistake and damage BT equipment. However, I am sure many readers
have at least wired their own extension and adding a modem is similar.
iii The 2b modem has a two-wire connection to BT, this is to the red and
white wires in current BT coding ie, pins 2 & 5 of the new wiper style
socket. If you have a Senator style multi-extension system this also
Wire your phone in parallel to the modem, the best way to do this would
be to wire an extension box with 2 sockets one for the phone, the other
for the modem. If you feel at all uneasy about this either get a BT
engineer who you know to do it, or get BT to do it officially.
iv For Nascom 2 owners with no R$232 control signals try and find out how
many control signals the modem needs, some may only require DTR which
could easily be faked.
5) More On UKM715
UKM715 as supplied by Henry’s is about 64K of source well commented with a
single patch area at the start. There are source copies either for Macro-80
or MAC, the Macro-80 version contains a Nascom 2 set of port numbers so
somebody has got it working. There is also an installation program UKINSTL
for those of you who get a .COM file which saves you assemblling it. For
those interested in telexing, a Telex utility is available called UKTLX.
6) Testing Your Handiwork
Having built all this marvellous equipment, what will it do? Well, every
month PCW prints a list of public access networks with tone standards and
operating times. The problem with quite a few of these is that they operate
only in the evenings when phone calls are a bit cheaper, most of them only