The FreeSpeak II protocol uses E1 + DECT sync signals (FSII-TCVR-19-EU or FSII-TCVR-19-US) Normal E1 converters do not pass the DECT sync signals. Therefore the antenna  needs to produce its own local DECT sync. By having the antennas produce their own local DECT sync, roaming between antennas is now limited and does not work correctly. Handovers between remote antennas is unpredictable and unreliable 

Handover means when the FSII BP is moving from one antenna to another. If the antennas are connected over Fibre or IP then when the FSII BP moves from one REMOTE antenna to another antenna the connection is not automatic and the FSII BP may first  drop the connection and go into searching mode before connecting to the next antenna

The connection method is -         Matrix >splitter > E1-to-IP<> IP-to-E1>antenna
There are several 3rd party E1-to-fibre or E1-to-IP converters on the market. You need to use E1 to TDM over IP converters. It’s important to use TDM converters !!! 
Attached are various E1 converters that several customers have used successfully in the past and within the limits of the reduced system performance and restricted handovers