The core at Cambridge, Massachusetts-based BBN Corp, the former Bolt, Beranek & Newman Inc, is getting ever smaller, and the latest to go is a business call routing service based on BBN’s speech recognition technology. The business is being shunted off into a new company, Parlance Corp, to be based in the Boston area and take with it about 30 BBN employees. The buyer is a Westlake Village, California venture capital outfit, Amerscan Inc. BBN will retain a minority position in the new company. No financial details of the pact were given.