*Result*: Phone call parameters measuring system for remote metrology.

*This paper presents the development and characteristics of a reference system for verifying the call parameter measurement subsystems of telecommunication networks. A key challenge addressed in this work is the accurate measurement of phone call parameters, specifically, the transfer of geographically distributed events—such as the initiation and termination of calls by end-users—to a centralized measurement point to serve as inputs for the reference system. To solve this challenge, the paper proposes and successfully implements an internet-based communication approach using the Session Initiation Protocol together with NTP and GNSS time-source implementation technicalities. The calibration methodology of the developed reference system is detailed, including the analysis of sources of systematic errors and uncertainty terms influencing the measurement process. Experimental calibration results for multiple devices demonstrate a systematic error of less than 0.1 ms in time interval measurement with an expanded calibration uncertainty of less than 12 ms. The adoption of the described call parameters measurement system not only supports Environmental, Social, and Governance objectives but also aligns with sustainable development principles by minimizing environmental impact, enhancing operational efficiency, and promoting long-term usability through open-hardware design and adaptability to future technological advancements. [ABSTRACT FROM AUTHOR]*