VoIP Trunking
Trunking is a concept in modern communications by which a communications system can provide network access to many clients by sharing a set of lines or frequencies instead of providing them individually. This is analogous to the structure of a tree with one trunk and many branches. Examples of this include telephone systems and the VHF radios commonly used by police agencies (from Wikipedia »).  The Checkmarq VBX-Series supports ISDN BRI trunks (2 channels per port) in the default configuration, and ISDN PRI (up to 30 channels per port) trunks with optional modules. ISDN trunks from telephone companies all over the world are compatible with the VBX-Series modules. If a local telephone company can't deliver ISDN trunks, then you have the option to connect analog telephone line bundles using the FXO modules with the Checkmarq VBX-Series.
However, in the modern telephony standards, there is a more technical and cost efficient way of connecting your external phone lines to the VBX-Series; VoIP trunking. In co-operation with our partner Vovone, we made optimized and secure VoIP trunking available for the VBX-Series that are virtually unlimited in number of lines, based on IP network connections, like DSL, Fiber and even Cable. These VoIP trunks are only limited by the bandwidth that is available on these IP network connections, and calls can be optimized in bandwidth usage when using different voice codecs. For instance, the default G.711 codec, the voice codec that is used for conventional ISDN lines (BRI/PRI), consumes about 64kbps of bandwidth per call plus about 2kbps (= total of 66kbps) to put it into an VoIP packet and for the first call in a trunk we have about 16kbps 'overhead' bandwidth to setup and manage the virtual VoIP trunk, which results in about 14 possible concurrent VoIP trunk calls over a single 1mbps DSL line (16 kbps + (14 x 66 kpbs) = 940 kbps or 0.94 mbps < 1 mbps. In this case you still have the same voice/sound quality as with conventional ISDN trunks, so 14 virtual 'ISDN quality' lines for the price of a single 1mbit DSL connection cost. When using the G.726 codec, the same codec used worldwide by conventional telecom companies when routing international calls, you get 28 lines per 1 mbps DSL line, that's about the same as one ISDN PRI-30 line. And when using the GSM voice codec, which is the same voice codec as used with GSM cellular phones, you are able to get up to 67 concurrent phone calls per 1mbps IP internet connection, that is more than two conventional ISDN-30 PRI trunks for the price of a single 1 mbps DSL line... There are more voice codecs available for the VBX-Series as options, but we install default these three voice codecs (G.711, G.726 and GSM) since they are widely used, robust and more important; license free. Beware that only with real VoIP trunking the bandwidth overhead is only once per trunk. If you have non trunked VoIP connections per device, the overhead is added with each call. Find below more figures with different codecs, which will be updated when more codecs become available. So how does this work in the real world? Well, fairly simple. All Checkmarq Resellers are known to be Vovone resellers and IP Network connectivity resellers too, so they can deliver the certified Vovone VoIP trunking over selected IP network connections with your VBX-Series installation. Vovone can provide (regional) phone numbers in selected countries all over the world and/or port your existing phone numbers to their network., just like conventional phone companies do. You won't notice any difference; if you use the VBX-Series default G.711 (ISDN) voice codec, everything just will be the same as when you use conventional ISDN BRI/PRI trunks, except for you wallet... that one will feel the difference for sure. VoIP Voice codec bandwidth comparisation when Trunking calls:
G.711 (ISDN - PCM)
one call: 164333.75 bps/94.26 pps ( 82.1 kbps bandwidth)
two calls: 296171.60 bps/101.46 pps (148.0 kbps bandwidth) For every additional call: 131837 bps (65.9 kbps bandwidth)
Est. IP/VoIP Trunk overhead (Only first call when trunking): 32495 bps (16.0 kbps bandwidth)
Raw number of calls per megabit: 14
G.726 (DECT - ADPCM)
one call: 102412.85 bps/97.28 pps ( 51.2 kbps bandwidth)
two calls: 170242.49 bps/102.46 pps (85.1 kbps bandwidth) For every additional call: 67847 bps (33.9 kbps bandwidth)
Est. IP/VoIP Trunk overhead (Only first call when trunking): 34645 bps (17.3 kbps bandwidth)
Raw number of calls per megabit: 28
GSM
one call: 70958.16 bps/102.13 pps (35.4 kbps bandwidth)
two calls: 100455.23 bps/102.63 pps (50.2 kbps bandwidth) For every additional call: 29497 bps (14.7 kbps bandwidth)
Est. IP/VoIP Trunk overhead (Only first call when trunking): 41461 bps (20.7 kbps bandwidth)
Raw number of calls per megabit: 67
G.729 (License fee apply)
one call: 60124.33 bps/101.26 pps (30.0 kbps bandwidth)
two calls: 79496.23 bps/102.85 pps (39.7 kbps bandwidth) For every additional call: 19372 bps ( 9.6 kbps bandwidth)
Est. IP/VoIP Trunk overhead (Only first call when trunking): 40752 bps (20.3 kbps bandwidth)
Raw number of calls per megabit: 102 Note: When measuring bandwidth, "kilobit" is 1000 bits per second (not 1024) and a megabit is 1,000,000 bits per second | 
