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The TSoIP system like so much else was born out of necessity. With the release of the Cisco LMR feature set, and the advancement in multicast usage, the radio world could now remotely control radio assets from virtually anywhere on the globe. What was not available however, was a system that made best use of IP and multicast for selective calling (selcall). With a large percentage of customers requesting this functionality, CISTECH set about creating a feature rich Interface and end point device to satisfy their requirements. See Figure 1 for a depiction of the end point device.
Traditionally, selcall systems required 32K of bandwidth for each channel to maintain a selcall tone sequence without any degradation. With the advent of higher compression codec's such as G729 (8K), voice traffic could now be passed over a network with a much lower bandwidth requirement. Unfortunately, as these codec's impair the integrity of the selcall tone sequence, CISTECH created an IP packet representation that is little bigger than an IP 'ping' packet requiring very little network bandwidth to overcome the problem.
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