Journal of E - Technology Dragan Martovic, Zoran Velikovic, Zoran Milivojevic, Marko Velikovic 12 4 2021 https://doi.org/10.6025/jet/2021/12/4/103-109 https://www.dline.info/jet/fulltext/v12n4/jetv12n4_1.pdf We studied the VoIP services with the integrated telephones with the emphasis on the features and ability. We have used an adapter Grandstream which is the analog telephone and the integration is studied. We have studied the performance of VoIP services by identifying the value of key quality parameters. We observed that the mean value of the jitter is oscillated around the allowed value. It should be noted that the Jitter was successfully compensated by the receiving buffers and had no influence on the conversation speech. During the trials it is observed that the key QoS parameters defined for the conversation speech were reasonable. It is possible to confirm the successful integration of analog telephones into the VoIP service which is the crux of this work.