Tyco International Ltd., still recovering from scandals that saw its longtime former chief executive sentenced to prison, said Friday it planned to split into three public companies.

Tyco is separating its electronics and health care businesses from its remaining operations, which include security and fire-protection services.

The company, which may be best known for its ADT home alarm systems, also warned that its first quarter and full-year 2006 earnings from continuing operations would be lower than expected. It estimated the cost of the breakup, planned for early next year, at $1 billion.