The cash offer, which is pitched at 325p a share, values SDX at pounds 124m - a massive increase in value since the company agreed a management buyout from Northern Telecom, the telecom equipment company, for about pounds 5m in 1991. The bid is also double the price at which SDX floated on the stock exchange in 1996.
Frank Bretherton, the chief executive, has a stake of about 9 per cent in the company, which yesterday's bid values at pounds 10.79m. Marketing director Jeremy Cooke will receive pounds 4.4m while Robert Kennedy, a former finance director, will pocket pounds 5.07m. Maurice Pinto, the non-executive chairman, gets pounds 2.68m.
Mr Cooke said that SDX had first started talking to Lucent in April, before announcing that it was in talks last month. He said that being part of a huge US company would give SDX the muscle to compete overseas.
"We can put our products through their channels worldwide," he said, adding that Lucent's huge research division and brand-name would be an added bonus. No jobs would be lost as part of the takeover, he said.
Lucent, meanwhile, gets the benefit of SDX's telecom technology, which is aimed specifically at small and medium-sized businesses. Bill O'Shea, the president of Lucent's business communications systems division, said: "SDX brings additional strength to Lucent in certain key products and technologies."
The company has taken market share from giants such as British Telecom with its Index technology, which allows companies to operate voicemail systems.
The directors, who between them control more than 20 per cent of the share capital, have agreed to accept the offer. However, analysts said a higher bid from a competing telecom company was still possible. The shares closed down 2p at 326.5p - still a premium to the offer price.