The present invention provides prodrugs of compounds that inhibit the activity of plasma kallikrein and methods of preventing and treating plasma kallikrein dependent diseases or conditions, for example, diabetic macular edema, with the prodrugs having the formula:. To this end, a connection device is provided with a base body that can be mounted in a terminal box socket of the electrical machine. The output symbols are generally independent of each other, and an effectively unbounded number of output symbols can be generated, if needed.