A system for communicating through a public telephone network includes a terminal side adapter which connects either a telephone set or a non-telephone terminal (such as a gas meter terminal) to the telephone network. Communication with the non-telephone is normally scheduled during the early morning hours to minimize conflict with normal telephone usage. Communication with the non-telephone terminal is initiated from a data center. A center side adapter unit makes a predetermined sequence of calls during predetermined time zones, and each of these calls is quickly interrupted without being answered at the terminal side. However the sequence of interrupted calls signals the terminal side adapter unit to telephone the data center and to connect the non-telephone terminal to the telephone network. If the terminal side adapter unit receives an incoming call outside the time zones, or if a call received within a time zone is not quickly interrupted, the incoming call is routed to the telephone set.