A method and an intermediate element, or a gateway, for routing an information flow in a telecommunication system including a plurality of switching centres. The switching centres are connected with an Internet Protocol (IP) based connection via the gateways, which are arranged to perform speech coding/decoding for an information flow between the switching centres. The gateways are further arranged to detect if the information flow from the switching centre is a data call and to omit the speech coding if the information flow is a data call. The data call detection is performed based on of a symbol pattern included in the frame structure of the information flow.