District Election Officer (DEO) – supervises the election work of a district. Returning Officer (RO) – of a parliamentary or assembly constituency is responsible for the conduct of elections in the parliamentary or assembly constituency .Electoral Registration Officer (ERO)- is responsible for the preparation of electoral rolls for a parliamentary / assembly constituency. Presiding Officer – The Presiding Officer with the assistance of polling officers conducts the poll at a polling station. Observer – the Election Commission of India nominates officers of Government as Observers (General Observers and Election Expenditure Observers) for parliamentary and assembly constituencies. They perform such functions as are entrusted to them by the Commission.