Dial inbound meter interface unit which derives power from telephone line when telephone is ringing

Claim 1

An MIU (meter interface unit) which is capable of deriving its power from a telephone line and capable of data transmission to a central computer over the telephone line, said MIU comprising: (a) means for receiving data; (b) means for transmitting data; (c) means for determining the time at which said means for receiving data and said means for transmitting data are to be active; (d) means for coupling a telephone line to said data transmitting means, said telephone line alternatingly maintaining an on-hook and an off-hook condition; (e) means for obtaining a DC current from said telephone line, wherein a DC leakage current is obtained during an on-hook condition and a DC current greater than said DC leakage current is obtained during an off-hook condition; (f) means for obtaining an AC current from said telephone line during an on-hook ringing condition; (g) long term storage means for storing a charge derived from said DC current and from AC current, wherein said long term storage means is capable of energizing said interface unit throughout the duration of said on-hook condition, and wherein said determining means is continuously energized by said long term storage means whenever said telephone line is in said on-hook condition.