The CS-5000 series(the launch of whose CS-5600 prompted this review) is a VoIP platform, based on a Linux kernel. There are three variants in the range, each of which is basically a superset of the entry-level CS-5200.

I’ve come across Inter-Tel’s Axxess range of phone systems over the last few years in my “day job” as a consultant and freelance software developer. The Axxess is what you’d call a “traditional” PBX – a chassis-based PBX that you slot feature cards into, of which the VoIP option (the “IPRC” card, as they call it) is just one. The CS-5000’s takes a different tack, though, with the emphasis firmly on VoIP at the core.

The CS-5200 is a blue 1U box with a small LCD display on the front alongside some buttons that let you do some basic functions like setting the device’s IP address or rebooting it. There’s also a socket where you insert a RAM card that acts as the voicemail repository. On the back of the unit are a pair of analogue RJ-45s; one drives a pair of analogue trunks (ie you can connect it to a pair of analogue phone lines as your external service) and the other a pair of analogue extensions (so you can hang a couple of traditional phones, or more likely modems/fax machines, off the unit). Obviously you’ll need to break out each individual RJ-45 into two sockets on your patch panel, but that’s a simple cabling job. Next to this are the interfaces for paging services and music-on-hold, and then you have the slot for the processor card (which has an Ethernet interface for connecting to your LAN). You then have three slots into which you can put trunk cards; each card can handle a pair of ISDN2s (i.e. four channels) or a single ISDN30, though there’s a dual ISDN30 module due for launch shortly. Oh, and if you need more analogue extensions, you can put a four-port analogue module in one of the slots. Oh, and the unit comes with a built-in 4-channel voicemail (i.e. four calls can be talking to the voicemail memory at once) and a simple licence change ups this to eight channels. There’s also built-in CTI capability via the OAI protocol.

The CS-5200 supports up to 75 IP endpoints (ie handsets). The "up to" bit needs a bit of clarification, though. When you connect an IP phone, you can set it to use either G.711 or G.729 signalling.

G.711, because it’s not being compressed to death, requires little processing effort, and so there should be no problem having 75 concurrent calls. G.729, on the other hand, is heavily compressed and uses a lot of processing power; thus, if you’re using G.729 on every handset, you can expect to have a limit of about 25 concurrent calls because the processor Is having to work hard.

You can mix-and-match protocols, though, so in reality you’d use G.711 on your LAN-based handsets (you don’t need to compress stuff as bandwidth shouldn’t be critical) and G.729 on handsets in, say, home or remote offices, as they’re talking over the WAN and probably need some compression. Thus the concurrent call limitation is unlikely to bite you unless you have shedloads of home/remote workers all making calls at once.

The CS-5400 is basically a CS-5200 on steroids. It ups the extension count to 175 by adding a daughterboard with extra processing power. It therefore looks the same as a CS-5200, but has a bit of extra kit inside to ramp up the call processing power.

The CS-5600 adds to the CS-5400 via an external 1U blue box, connected via Ethernet, which has yet more processing power for handling compression (the CTI effort is also off-loaded to the external box to leave the main CPU a bit more free to do “proper” work). This puts the extension count up to 250, and you also gain some extra voicemail channels – eight out of the box, plus another eight if you pay for the additional licence.

Generally speaking, you’ll connect IP handsets to the CS-5000. They start at £80 for a simple one, though most installations have slightly posher ones with two-line LCD displays, which come in at £140. There’s also the choice of an eight-line display, which will set you back £210. Oh, you’ll also need a £60 licence for each handset. The handsets are PoE-capable, but if you don’t have PoE in your LAN infrastructure, you simply buy an adaptor that plugs into the mains and supplies the power. You can also use Inter-Tel’s standard digital (i.e. non-VoIP) handsets if you so wish – they’re the same price as the IP ones (except you don’t need the extra £60 licence), but you’ll need to add an extra 1U blue box that connects to a port on the back of the CS-5200 chassis and provides the IP-to-non-IP conversion.

Each CS-5000 system can link to other CS-5000s or to the Axxess range, so you can have multiple physical PBXs which appear to the user to be one big phone system. If you wish, the CTI data streams can be aggregated in a gateway – each event message includes a flag showing which PBX the message came from. The only caveat is that the administration program (a Windows-based application called DBAdmin) differs between the CS-5000 and the Axxess. The two applications actually look identical – you really can’t tell the difference – but you can’t run the CS-5000 admin program to manage an Axxess, or vice versa. The reason is simple – the architectures of the two systems, even though they’re completely interoperable, are completely different beats. At least they’ve made the two management apps look and work the same, though.

Are there any negative points? Just some minor ones. First, although DBAdmin is versatile and fairly simple to use, there’s a lot to get to grips with and the GUI can be a bit clunky. Second, although these systems are ridiculously inexpensive, don’t think for a minute that just because it isn’t costing much, you can order one and plug it in yourself. This is particularly true if you’re sitting the unit behind a NAT firewall and you’ll be using home-worker VoIP handsets – it works great, but you need to know what settings to play with (when I first did it it took a packet-sniffer and a long phone call to a specialist to figure out what we were doing wrong!). Expect to pay a reseller for a few hours of time to install the box for you, then. Also, to make the most of the unit you should really spend some money on a short training course to learn what all the bits do and how to administer it properly.

It’s no surprise that I like the CS-5000 range. Okay, you have to think a bit about the concurrent call limitations, but I quite like the way they’ve done it. After all, the CS-5200 was originally sold as having a 25-user limit (to reflect its call capacity) so what they’re achieving by upping the limit is to say: “Look, if you have maximum compression on everything, you’ll still have the 25-user limit, but if you don’t need that, we’ll let you use the capacity”. Add up the excellent CTI capabilities, the attractive price, and the fact that you can start with a CS-5200, then upgrade that to a 5400, then upgrade that to a 5600, then maybe integrate it easily with additional ones, and you have a scalable system too.


Don’t forget to factor in the installation/training costs, because if you’ve got any sense, you’ll want some of both.