PSTN stands for a public switched telephone network. A PSTN gateway is hardware components that third parties use to translate signaling.
The specifications for a PBX Phone systems can vary depending on the computer, things to be taken into consideration are, operating environment, PSTN Signalling, Management, Concurrent capacity, voIP signalling.
You will need a media gateway in order to connect a GSM network to PSTN lines without the need for a PBX or key system.
H.323 gateway. network + page 561
MGC or MEDIA Gateway Controller, it handles the connection to the PSTN (telephone system) from the computer VOIP side.
By the way, call from VOIP can be received by pstn modem. But pstn cannot make a call to VoIP number.
Answer B H.323 gateway (A device that provides translation between network devices running H.323 signaling protocols and devices running other types of signaling protocols (for example, ss7 on the PSTN). Page 548
differentiate between PLMN and PSTN in brief in wirless communication
disadvantage of in-band signalling
A normal MSC will connect BSC to the PLMN/PSTN Network directly. Meaning to say it will need to do the call connections and management from BSC all the way to PLMN/PSTN network. Once the network expands, the MSC will face congestion and therefore a solution needed. GMSC - Gateway MSC, as the name implies, will in this case serve as an interconnection between MSC and PLMN/PSTN Network. Thus this free up the resources of the MSC itself need to perform all the originally tasks.
ISDN is dial up lines and PSTN is a broadband line.
Cellular Signalling was created in 1989.