This part of IEC 62055 applies to newly manufactured, static watt-hour payment meters of accuracy classes 0,5, 1 and 2 for direct connection, for the measurement of alternating current electrical energy consumption of a frequency in the range 45 Hz to 65 Hz that include a supply control switch for the purpose of interruption or restoration of the electricity supply to the load in accordance with the current value of the available credit maintained in the payment meter. It does not apply to static watt-hour payment meters where the voltage across the connection terminals exceeds 1 000 V (line-to-line voltage for meters for polyphase systems). It applies to payment meters for indoor application, operating under normal climatic conditions where the payment meter is mounted as for normal service (i.e. together with a specified matching socket where applicable). Payment meters are implementations where all the main functional elements are incorporated in a single enclosure, together with any specified matching socket. There are also multi-device payment metering installations where the various main functional elements, such as the measuring element, the user interface unit, token carrier interface, and the supply control switch are implemented in more than one enclosure, involving additional interfaces. Functional requirements that apply to payment meters are also defined in this document, and include informative basic functional requirements and tests for the prepayment mode of operation in Annex A. Allowances are made for the relatively wide range of features, options, alternatives, and implementations that may be found in practice. The diverse nature and functionality of payment meters prevent the comprehensive specification of detailed test methods for all of these requirements. However, in this case, the requirements are stated in such a way that tests can then be formulated to respect and validate the specific functionality of the payment meter being tested. ...