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On-Site Pbx Designed primarily for those organisations wishing to integrate legacy PSTN lines with VoIP, an on-site IP-PBX is installed at the business premises and managed in its entirety by the user. As well as an IP-PBX, a VoIP-PSTN gateway is required to route and convert analogue or ISDN calls to VoIP (Figure 2). Figure 2: An on-site IP-PBX VoIP telephony system
Hosted IP-PBX disadvantages χ Significant up-front capital expenditure is often prohibitive or deemed to be too high, especially by businesses using VoIP telephony for the first time χ Hardware maintenance and upgrades are an ongoing expense, requiring engineering slots with the provider/manufacturer, as well as inhouse technical expertise χ Flexibility, scalability and ‘bespokability’ are limited by the physical hardware χ Increasing the number of users is not straightforward and can be a complex process, particularly if the system has already reached the maximum number of allowable users. This in turn reduces the suitability of an on-site IP-PBX for companies, including those, which are growing or plan to do so χ Licensing costs for upgrades and additional users can be high even if the hardware is capable χ Support for homeworkers may be limited as it is reliant on the site housing the system and the available bandwidth
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Cost of ownership reduces over time, with lower operational expenditure and savings over the course of several years No monthly subscription payments, because you have purchased the system outright
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More control over the feature set and call routing (if using an open-source platform such as Asterisk)
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No need to change current call carrier because an on-site IP-PBX can connect to the PSTN, which in turn minimizes procurement changes
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PSTN can easily be used as a failover when Internet bandwidth is limited or disrupted
χ Failure or loss of the PBX will mean incoming calls get a busy tone, indicating that no transmission path to the called number is available. This can potentially lose sales and damage a professional reputation χ Physical disasters or power/broadband outages at your premises will put the PBX and therefore the phone system out of action χ The IP-PBX is a single point of failure that could lead to significant downtime χ Business premises rarely offer the resiliency and protection of a purpose-built secure data centre, potentially exposing the phone system to greater risk χ Additional space will be required to house the system, along with racking and cooling χ The full potential of the system may never be realised due to relatively limited in-house technical knowledge. This will minimize the benefits gained from VoIP telephony and the investment itself
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