80-Bus News |
July–August 1984, Volume 3, Issue 4 |
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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 – 3; 4 – 4; 5 – 5; 6 – 6; 7 – 7; 8 – 8; 20 – 20.
Now comes the dodgy bit:
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:
| i | 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
phone.
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
works.
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 RS232 control signals try and find out how many control signals the modem needs, some may only require DTR which could easily be faked. |
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.
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
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