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after the changeover to digital systems there was a period when loop disconnect was recognised, with the passage of time the likelihood is that it all changed to dtmf only. the dial breaks are probably seen as some sort of command and gives the nut or whatever tone you are hearing. scorpion electronics in kells co meath sold a dtmf machine i dont know if they are still in business.alternatively buy a cheap phone and gut it for the tone generator and keypad . regards EI7KA