Signal Processing Functions (SPF) designed for speech quality, when located in the network, may interact with in band signalling (e.g. TFO) and non-voice services (e.g. HSCSD). The platform that carries these SPFs is called Signal Processing Network Equipment (SPNE) and may therefore need to provide mechanisms/auxiliary functions to support in band signalling and non-voice services depending on where in the network the SPNE is going to be deployed and what services and/or in band signalling are present. This Recommendation defines these mechanisms/auxiliary functions of a Signal Processing Network Equipment (SPNE) designed for the use in the circuit switched part of a network (mobile, fixed and hybrid).