When using the C-2000B in the “Analog Station” mode, it distributes the dial tone to the four entry points and the C-2000B is always monitoring for a “CPC” (momentary break) from the phone line connected to terminals 6 and 7.  When you press the call button on an E-30 and the C-2000B detects a CPC break, the C-2000B will provide 3 beeps to the E-30 and then provides a CPC to the E-30 to disconnect it.  The C-2000B is detecting a CPC from your phone line (or PBX extension) at the beginning of the call that is not intended to be a disconnect break (may just be a connection break).  The newer C-2000B’s have a way to fix this in programming, described on page 18 of the product manual under “enable/disable analog station CPC detection” (the “#65” position).  You want to access the program mode of the C-2000B and program “0#65” to disable analog station CPC detection.  This is only available on newer C-2000B’s with a part number (P/N) that ends with a “D” or “E” (this can be found on the serial number label).  Older C-2000B’s can be updated in the field to the latest software by ordering a part number “C2KC”.  There is a charge of $30.00 for the software and it can be ordered through technical support or an authorized distributor.