Known issue with the Bogen VoIPs where static is heard when a combination of a multiport unit and single port unit is used.

In order for the quality to be the best you should make sure the CODER selection is set to G.711 U-law on each side. This is found under the VOICE/FAX menu. This issue can be fixed by disabling silence compression on both sides or by loading special firmware on the multiport side of 6.08.DB and setting the input gain to mute on the MVP130 side. With the firmware method the silence compression can be enabled.

Here is the firmware link: