Protocol's

H.323 PROTOCOL is an overall recommendation that includes references to other network standards like H.225 and H.245 of ITU (International Telecommunication Union), which sets network standards for multimedia communications over packet-based networks that are not able to provide a guaranteed good Quality of Service (QoS).

H.323 PROTOCOL defines various entities, which make possible media and multimedia communications using endpoints, multipoint conferencing units or MCUs, gatekeepers, and gateways and their interaction.

PBX or PRIVATE BRANCH EXCHANGE is a specialized telephone system, which is used in both private and governmental organizations and companies to manage external and internal calls. Advantage of PBX is that the organization using it does not requires a different phone line for each of their phones and internal calls do not go outside and are not billed.

PULSE CODE MODULATION or PCM converts sound or voice analog signals into digital signals, so that these signals can be processed easily by a digital device, for example, a computer. You also need to use a codec if you want to compress the results for transmissions to occupy lowest possible bandwidth.