STS is the Standard Transfer Specification, an international standard recognized and issued by the International Standards Institute. It was first developed in South Africa. In 1997, STS Association was established in South Africa, and in 2005, it was standardized as IEC62055 by the International Standards Institute. It’s mainly to provide reference for the realization of electricity meter encryption, decryption and prepayment.

STS code-type prepaid electricity meters transmit a series of instructions such as electricity purchase code (Token), encryption and decryption, and key management according to this specification. The electricity meter that supports STS protocol has the characteristics of unique key, unique token, and unique verification, so as to ensure the uniqueness and security of the token.

The STS meter has all the functions of prepaid meter. Prepaid meter means that the user buys electricity first and then uses it. When the user runs out of electricity, the relay will automatically disconnect so that the user cannot continue to use electricity. After the user buys new electricity, the relay will automatically close and user continue to use electricity, which solves the problem of the difficulty of charging for the utility company.

STS meters use token to manage electricity. A token is an STS (Standard Transfer Specification) compliant 20 digit number issued upon purchase that will release the specified amount of electricity (in Kwh) on the STS Smart Prepaid Meter. Using token can avoid the cost of printing and purchasing IC cards. Users can obtain the electricity purchase code and complete recharge by themselves through printing note, text message, or the network.

There are two types of token prepaid meters: all-in-one and split-type. The all-in-one meter is the integration of the token keypad and the electricity meter. You can only need to press the keypad on the meter and input token to complete the interactive functions related to the meter. The split-type meter is the token keypad and meter split. One keypad can be connected to one or more prepaid meters. This keypad (Customer interface unit) can be installed indoors or outdoors, and the meter can be hidden in the pole meter box.