The voice channels were designed for communication among multiple offices of a single company. As such, the levels obtained from the various telephone instruments of that private network will normally be consistent within a few dBms. Under these conditions, the input level adjustment procedure is based on a signal source (speaker) of a 1004 Hz tone at 0 dBm.
Where regulations allow, the voice channels may connect directly or indirectly to the Public Switched Telephone Network (PSTN), presenting a different set of conditions. Here, the calls may originate from widely different sources with extreme variations in signal levels (up to 20 dBm). Further, the levels from calls within an office will often be different from the PSTN levels.
Therefore, it is strongly recommended that voice channels be dedicated either for private network use or for PSTN use, but not both.
If the planned usage for a single voice channel is both private network and PSTN operation, then one of the applications should be selected as the primary use, and the voice channel aligned for that purpose. The secondary application should be validated to determine if a compromise setting is required.
The telephone equipment to which a voice channel is attached should be installed and made functional. If the telephone equipment is not installed, then the installation should be scheduled after the telephone equipment is installed and configured, or a joint installation should be scheduled (as a last resort).
Make sure that an asynchronous ASCII terminal or equivalent is connected to an asynchronous port on the unit. This terminal will be used for configuration and testing in the subsequent adjustment procedures.
As described previously, every adjustment procedure described here involves a local pair of voice channels. The voice pairings treated here follow the most common voice applications, as follows:
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