This module converts HDB3 E3/E2/E1 to digital clock and data, and/or converts digital clock and data to HDB3 E3/E2/E1. The <rate> parameter must one of: E1: 2048000 Hz E2: 8448000 Hz E3: 34368000 Hz T1: 1544000 Hz (requires crystal option) T?: 32768000 Hz (requires crystal option) The <gain> parameter can introduce 0, -3, -6, or -9 dB of attenuation. This upper SMB is input, the lower SMB is output.