Abstract: A tone source is automatically adaptable in operation to generate tones as required for virtually any TDM telephone system in accordance with stored tone samples being defined to meet the requirements of a particular one of the telephone systems. The tone source provides encoded tone samples from a ROM wherein each tone sequence is stored at corresponding sequential address locations. Each sequence is terminated at unique first and last address locations. The last address location is followed by an address location having an end-of-tone code stored therein. A sample of each of the tones is progressively fetched from the ROM in response to each frame occurrence in an associated operating telephone facility. The first address of each sequence is stored at a corresponding index address location in the ROM. In response to each end-of-tone occurrence the index address of the instant tone sample is read from the ROM and used as a starting point for subsequent fetches.