Digital

Signal Flow

The level adjustment involves a pair of connected digital voice/fax channels within the same T1/E1 Voice Module, or a pair of channels within the same BRI Voice Module (BVM). Both channels are initially set for 0 input level gain and 0 output level attenuation. Then, a signal from a fixed 0 dBm source is applied in one direction through the connected pair. At the voice/fax channel nearest the signal source the input level is adjusted for -4 dBm.

At the other voice/fax channel the output signal is monitored. If the signal falls between -8 dBm and -16 dBm, no adjustment is necessary. If the level is higher than -8 dBm (for instance -6 dBm), attenuation is added until the level falls to -8 dBm. In a properly operating DVM/BVM and PBX the signal level will not fall below -16 dBm.

Equipment Required

• Two MetroTel Model VNA-70A Voice Network Analyzers (VNA) or equivalent, capable of generating a 1000-Hz tone at 0 dBm. When in the receiving mode, the analyzer must provide a 600-ohm termination and display the value of the measured signal strength.
• One asynchronous terminal operating at 9600 bps.

Note: These procedures are intended for equipment operated outside of the U.S.A. and Canada, and must meet the standards of the country wherein the equipment is used. Perform these procedures only if your country does not require specific input and output level settings.

The following topics are discussed in this section:

• Preliminary Procedures
• Adjusting Voice Levels