Paging volume levels changing with number of phones

I am using * 1.4 with 6 POTS Phones on 6 ATAs on a private LAN.

  1. Invidiual Paging
    *1 pages Phone 1 on ATA1
    *2 pages Phone 2 on ATA1

    *6 pages Phone 6 on ATA1
    Individually the pages work fine.

  2. Group Paging
    *12 pages Phones 1 and 2
    *123 pages Phones 1, 2 and 3

    *123456 pages Phones 1, 2, 3, 4, 5 and 6
    As more and more Phones are added to the Page, the sound level becomes proportionally louder. The increased volume, with 5 or more phones in the group, is so distorted it cannot be understood.

Can the volume be adjusted for Paging?

Thanks.