The present invention is a dial in-bound MIU capable of deriving its operating current from a telephone line. The MIU is coupled to the telephone line using conventional practices. The MIU has the capacity to initiate data transmission at a predetermined time or upon demand by the customer or the utility...http://www.google.com/patents/US5454031?utm_source=gb-gplus-sharePatent US5454031 - Dial inbound meter interface unit which derives its power from a telephone line
