It is the aim of the present paper to analyze the perceptual quality dimensions of modern telephone connections. Such connections differ from standard connections in their time-variant characteristics (e.g., due to Voice-over-IP transmission or due to noise reduction algorithms) and their user interfaces (e.g., hands-free terminals). With the help of two independent auditory experiments with subsequent multidimensional analyses, three perceptual dimensions were identified for a diverse set of stimuli. These dimensions were labeled "directness/frequency content", "continuity", and "noisiness". Overall listening quality scores were collected in a separate experiment. A mapping of the obtained dimensions onto the overall listening quality scores by means of a linear model revealed that "continuity" appears to be the most important dimension in terms of overall listening quality.