Advent International and Apax Partners, two private equity firms, have sold UK-based Tertio Telecoms, a telecoms software company, to Evolving Systems, also a software provider, for $40.7m in a rare exit for venture capital investors.

Evolving Systems put up $11m in cash to fund the transaction along with $16m in seller-financed notes, debt funded by the vendor, and $13.7m in convertible preferred stock. Evolving Systems may convert the vendor debt to a convertible note early next year.