for some time to come. PC Based-Server Gateways Based On Industry Standard Voice CardsThe first IP telephony gateway products were based on industry standard voice cards such as the Dialogic series voice cards. These cards are designed to play and record announcements to callers, and are typically used in office voice mail or interactive voice response systems. These vendors had the benefit of being able to get their products to market quickly. However, these systems also have some important limitations: Industry standard voice cards are not designed for real-time applications like IP telephony. The IP telephony software must deal with audio in discrete chunks rather than as a continuous stream. This introduces latency (delay) into a conversation. Industry standard voice cards are not designed to compress and decompress audio. This means the host PC containing the cards must do all of this processing on the host CPU. This also introduces latency, and limits the scalability of the gateway to no more than a few simultaneous conversations. Industry standard voice cards are generally not very easy to install and configure; they are not plug and play cards. Many of these systems use proprietary protocols to deliver phone calls, which means you are locked into one vendor's solution. At US $1000 to US $2000 per port, these solutions are on the expensive side. These gateway servers, while they served an important role in the market (i.e. they were the first working products to hit the market), have a limited future since they use hardware which was never designed for this kind of application. In order to remain viable, vendors using this design will need to shift to hardware that is designed specifically for IP telephony. PC Based Server Gateways Based On Specialized DSP CardsOnce the concept of the IP telephony gateway was proven, vendors sought to address the shortcomings of the existing voice cards by engineering cards specifically for ...
