On 16 December 2015 at 18:30, John Gardner <gof...@gmail.com
<mailto:gof...@gmail.com>> wrote:
Historically, telecom regulation in the UK was rather
different
than what we're used to - Television receivers
required licenses,
for instance. Data was charged for by the byte. I'm
speculating
that built-in modems may have (had) some similar
dis-incentive
built-in for the manufacturer or retailer.
One of the *big* things here in Australia that caused issue with the
Telecom Approval process was that the specific line isolation
transformer used in the machine was considered too small and therefore
unable to provide the 3KV isolation that was required, so it was never
approved. In the same era, modems here were pretty big.
Another issue would have been that the modem used Bell 103 tones, not
CCITT v.21 which was standard in Australia (and probably the UK), so
that was also unacceptable.
I remember spending ages experimenting with resistors and capacitors in
the active bandpass filters within the modem to allow CCITT tones to
operate. It worked reasonably well, but was never perfect.
Doug
--
Doug Jackson
Dougs Word Clocks.com Pty Ltd
www.dougswordclocks.com
