An electronic display comprising: a housing; a display panel within the housing and having a display surface that is visible through the housing; an electronic processor arranged to control functions of the display and operating conditions within the housing; input sensors (306,307) disposed within the housing at distributed locations and arranged to sense operating conditions within the housing; output components (101,102) disposed within the housing at distributed locations and arranged to respond to control signals, the output components including at least one variable speed fan (101,102); characterised in that: the electronic display further comprises: a plurality of modules (306A,124,125) each providing a unique address identifier and at least one connection to one of said input sensors (306,307) and output components (101,102); and a bus connecting said modules (306A,124,125) and electronic processor for intercommunication: wherein, in use: processing of signals received from said input sensors (306,307) and control signals passed to the output components (102,202) is distributed amongst at least one microcontroller (306B,124B) on each of said modules(306A,124,125); and the electronic processor uses the unique address identifier of at least one said module (306A,124,125) to: receive a temperature reading from at least one module connected to a temperature sensor; process the temperature reading to determine at least one new fan speed setting (101,102); and send data to a module (124,125) to set at least one fan speed (101,102) to the new setting via the bus. a housing; a display panel within the housing and having a display surface that is visible through the housing; an electronic processor arranged to control functions of the display and operating conditions within the housing; input sensors (306,307) disposed within the housing at distributed locations and arranged to sense operating conditions within the housing; output components (101,102) disposed within the housing at distributed locations and arranged to respond to control signals, the output components including at least one variable speed fan (101,102); characterised in that: the electronic display further comprises: a plurality of modules (306A,124,125) each providing a unique address identifier and at least one connection to one of said input sensors (306,307) and output components (101,102); and a bus connecting said modules (306A,124,125) and electronic processor for intercommunication: wherein, in use: processing of signals received from said input sensors (306,307) and control signals passed to the output components (102,202) is distributed amongst at least one microcontroller (306B,124B) on each of said modules(306A,124,125); and the electronic processor uses the unique address identifier of at least one said module (306A,124,125) to: receive a temperature reading from at least one module connected to a temperature sensor; process the temperature reading to determine at least one new fan speed setting (101,102); and send data to a module (124,125) to set at least one fan speed (101,102) to the new setting via the bus. receive a temperature reading from at least one module connected to a temperature sensor; process the temperature reading to determine at least one new fan speed setting (101,102); and send data to a module (124,125) to set at least one fan speed (101,102) to the new setting via the bus.