The invention relates to an interface multiplexer for connecting a printer to plurality of disturbance recorders and fault locators comprising plural it.), of input ports for connecting the output from the disturbance recorders and/or fault locators. The input ports are connected to a microprocessor and a mcmory is connected to said microprocessor. The memory has plurality of memory banks allotted to each input port. Indicating means comprising plurality of light emitting diodes is connected to said microprocessor for indicating the port which is being serviced at any moment of time and the health of the internal circuit of the device. An output port is connected to the microprocessor tor providing printable data received at each input port to the printer. The microprocessor is provided with data scanning means, data transfer means and sensing means.