1. A handsfree apparatus coupled with a phone and allowing a handsfree phone call via the phone, the handsfree apparatus comprising: a storage medium including a primary control program and a model-specific program, the primary control program being stored in a predetermined storage area for enabling the handsfree phone call when coupled with the phone, the model-specific program being stored separately from the primary control program and operated to resolve a model-dependent constraint by being incorporated in the primary control program, the model-dependent constraint arising when coupled with the phone, the storage medium further including a database storing (i) phone model information specifying a model of the phone and (ii) program specification information specifying the model-specific program independent of the phone model information, the database associating each of the phone model information, and the program specification information with the model-specific program; means for acquiring a device name as information when coupled with a phone, wherein when the device name was previously registered with the phone, the registered device name is enabled to contain a keyword as well as phone model information; means for retrieving a model-specific program, (i) when the database previously includes the phone model information contained in the acquired phone information, the retrieving means retrieving from the storage medium the model-specific program, which is associated with the phone model information contained in the acquired phone information, and (ii) when the database does not previously include the phone model information contained in the acquired phone information, the retrieving means regards the keyword, which is other than the phone model information and contained in the acquired phone information, as the program specification information and then retrieves the model-specific program associated with the program specification information as which the keyword contained in the acquired phone information is regarded; and means for executing the retrieved model-specific program by incorporating in the primary control program.