Abstract: A regulated power supply can be derived from a battery supply input and a regulator, but in order to conserve battery power, alternative power supplies can be provided each with a switch responsive to the regulator to connect that alternative power supply to the output when it rises to the level of the battery supply.

Abstract: A meter reader 12 analyzes a signal from a meter 22 and compares its structure with a plurality of known signal structures stored in a memory 41. If the comparison shows that a particular one signal structure stored in the memory is inconsistent with the data signal being received, that structure is rejected and not used in future comparisons as the receipt of the data signal progresses. Eventually, the non-rejected signal structures should be reduced to a single structure which by elimination must be the closest structure to that of the signal being read. The meter reader can then pass the received data signal and the identification of its particular signal structure to further processing apparatus 11 such as a signal recorder or signal display and can arrange this recording or display so that parts of the signal representing different properties can be arranged consistently with other data signals which may be of different structures.