| 摘要 |
A testing apparatus which is arranged to execute selectively commandable preprogrammed operations comprises a credit memory (12) for storing a credit balance and input means (14, 16) for inputting a credit code defining a predetermined credit sum into the apparatus which is arranged, upon an input of a credit code, to check the validity of said code (block 31) and, if the code is found to be valid, to increase the stored credit balance by the sum corresponding to said code (block 34), the apparatus being further arranged, upon a command for an operation subject to a charge, to check whether the stored credit balance amounts at least to a sum corresponding to the stipulated charge for said operation and to permit an execution of said operation only if this is the case (block 22) and to decrease the stored credit balance by said sum (block 26) in connection with the execution of said operation (block 25).
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