The following meter-specific tokens are used:
General token handling
During input the numbers entered are displayed on the LCD, scrolling from right to left, with a dash displayed at every fourth digit. A counter in the upper left corner shows the total number of entered digits.
In this example 15 digits have already been entered.
The delay for accepting an input of the next digit is 20 seconds. After that time the display returns to the default display and the token entry was incomplete.
After token input the display shows one of the following information for 3 seconds.
The Token is accepted and the purchased energy amount is added to the remaining credit.
After that the meter shows the purchased amount for 5 seconds.
If the input is wrong, or random numbers are input with the purpose of tampering, the LCD display will indicate Reject-x, x is the times of wrong input.
In this example have been already eight inputs wrong. After 3 wrong inputs the keyboard is locked for 10 seconds. During that time the display shows: REJECT and the remaining waiting time in seconds (toggles every two seconds). With each new wrong input the lockout time for the keyboard is doubled. After 10 wrong inputs the customer needs to wait 1,280 seconds. This is the maximum waiting time. Each new incorrect input leads to another waiting time of 1,280 seconds. When token entry lockout is active the interface does not decrypt any meter specific tokens. Non-meter specific tokens and codes are still accepted and processed as normal while in lockout mode. The lockout period is reset to its original non-lockout status after any meter specific token has been successfully accepted by the meter or after meter is powered down and up again.
A security feature built into the STS is that no credit token can be used more than once. This is achieved by having an identifier built into the token. These identifiers are stored in a table in the meter, and the identifier of a new token is compared with the table If it has already been entered into the meter, the token will be rejected. The meter will give a notification that the token is used.
Due to the nature of the token identifier, an STS token has an effective life-time of approximately three months. If a token older than three months is entered, the meter may reject that token, and give an indication on the display that the token is old.
Full: A meter has a maximum amount of credit that it can store. If the number of units on the token will cause the meter credit to exceed this maximum value, the token will be rejected. The token may be entered at a later date when the level of credit in the meter has reduced enough to accept this token. The meter gives an indication that it is full.