These interface units give the System 3505 Prism LX the ability to receive alarms over coded alarm wires. The TCI options decode any incoming speed telegraph code without adjustment and include automatic index detection (municipal or central station) plus box timing printouts on municipal boxes. Each TCI option will decode a one to six digit box of the standard 1:2.5:6.25 index for Municipal and 1:3:9 for central station. When the test open option is added, it provides a trouble indication. A prefix option is available to append the box number with the circuit number. This is useful if multi-system monitoring is performed where duplicate box numbers exist.