A GSM-PRI Gateway is an interface dto connect multiple GSM SIM Cards to an existing EPABX using a PRI interconnect.

30 SIM Cards are connected on the network side and a PRI line output on the EPABX trunk side line and in turn seizes one of the GSM SIM cards and out dials the number.

Similarly, when the SIM number is dialed by someone, then the gateway sends it via its PRI line and lands it on the designated extension of the EPABX.