Hello. My name is***** can help you with your question.
The transcribers that you have are compatible only with the M 2000 cassette recorders that are included with them when you purchase the transcribers. There is functionality on the M 2000 cassette recorder that does not exist on other cassette recorders and is required for the operation of the recorder with the transcription machines. If you want to replace the cassette recorders a came with the transcribers, you would have to replace them with the same model recorder.