Satchwell Controls, based in Slough, Berkshire, employs just over 1,000 and is Britain's biggest manufacturer and installer of automation systems for industrial and commercial buildings. Siebe is acquiring the business for cash and assuming its small amount of debt. Last year it made operating profits of pounds 4.9m on sales of pounds 60m.
In total the businesses being disposed of have sales of pounds 400m - less than 3 per cent of group turnover. Other likely candidates for sale include GEC's wire and cables business and office equipment subsidiary.
However, Mr Simpson, who took over from Lord Weinstock last September, is thought to have decided against selling off GEC's medical systems and semiconductor divisions and its 50 per cent stake in the Creda and Hotpoint consumer electronics business.
The disposal programme, part of a fundamental strategic review of all the group's operations and management structure, was outlined in December alongside GEC's interim results.
GEC has taken a one-off charge of pounds 160m to cover costs associated with the programme but none of this has been used in connection with the Satchwell sale.
Dr George Sarney, president of Siebe Control Systems, said Satchwell would become the flagship of its building automation operations in Europe and would provide the platform for future world-wide growth.
Satchwell's products range from air temperature sensors and valve actuators to complete computerised maintenance management systems.