In the 1980’s telephone technology achieved switching by physical cross-point matrices in small analogue key-systems with signalling for buttons being over a secondary pair of wires.  It was commonplace for two-pair cabling to have to be installed instead of the original CW1308 single-pair wiring.

In the early 1990’s Time-Division-Multiplexing moved out of the Phone exchange into PABX (Private-Automatic-Branch-eXchanges) & KTS (Key-Telephone-Systems).  Through digital extension cards the analog voice and signals were transmitted in bit that were decoded by the handsets and routed to the earpiece or indicators as appropriate.  Developments in LCD technology meant that now much more information could be displayed without any increase in the power being distributed to the extensions.  Now these display screens showed the time-and-date, the CLI of the caller or the number you’d dialled, as well as the duration of the call.

Also the 90’s saw the advent of CTI (Computer Telephony Integration) where applications were developed that firstly allowed outbound dialling from company databases, then popping records of incoming callers by recognising the Calling Line ID.  This was at the time that the ISDN (Integrated-Services-Digital-Network) was being rolled-out in ISDN2 and ISDN30 formats.  With integration with European standards these notations changed to ISDN2e & ISDN30e.  These digitised trunk lines enabled the development of video conferencing – mostly by pooling two channels to achieve the required bandwidth.

Since 1990 we’ve also seen 3G trying to oust GSM, Wi-Fi and DECT transforming mobility within offices followed by BlueTooth personal area networks linking mobiles to earpieces and Conference hubs to microphones and speakers.

As we write this article (April 2011) the BT 21^st Century Network is being slowly rolled out throughout the UK.  This is aimed at replacing all the existing phone circuits into homes and businesses with SIP Trunks that will deliver phone Calls, Emails, TV, Video-on-Demand, plus our usual Internet access.  The bandwidths will be greatly improved over that which Broadband gave you and rather than having download speeds of 1 or 2Mb we’ll all be experiencing over ten times more.  But beware – until the complete infrastructure is upgraded your conversations may be liable to drop-outs as in the emergent days of SKYPE.  But it’ll get there.

What phone technology will they think of next?