SDX

SDX was originally owned by STC which became part of Nortel.  This part of Nortel was bought as a management buyout.

It is thought that BT pushed the sale because Nortel was supplying BT with small and large telephone systems and that this could cause a conflict of interests.

SDX now run by it's own management strengthened the SDX range and bought out the Index range.

Lucent then bought the company and still market the Index range.

Lucent have now changed the name of the telephone systems side of the business to Avaya.