Abstract: Traffic signals at an intersection are controlled by one or more controllers of the state/interval type, located in the vicinity of the intersection. One or more remote units that are portable or mobile communicate with the controller via a coded signal to command specific light operations, instruct a secondary controller to take-over light control at the intersection from a primary controller, and to reprogram the operation of the controller on a temporary or permanent basis. The remote units generate a code that must be received accurately by the controller before commands are followed. In order to economically provide such a code, the code generator employs a diode matrix that orders data words and address words and is easily reprogrammed. The traffic signal indicator operation is monitored by the controller both to detect controller error, as by a voltage error resulting from an incorrect controller action, and to detect a non-controller error, as by a current error resulting from a burned out indicator.