Thanks for your PM, glad we cleared the air.
Some useful background on some of the gateway possibilities here ...
http://www.voip-info.org/wiki/view/VOIP+GSM+Gateways
If you can provide a bit more info about the proposed usage (number of users, type of connection available, interfaces to any existing equipment, budget available, etc etc) then we can firm up on some further ideas.
Here are some questions for prospective gateway clients
1. What is the budget?
This should be your first question. You'll need to know the gateway's cost in order to match it against products with similar feature sets. Be sure to factor in any additional support costs.
2. Is the Gateway Hardware or Software-based?
Many businesses buy hardware-based gateways because they're perceived to offer stronger security protection, are more reliable and provide better connectivity. The software type, tend to cost less and can be easier to update and modify.
3. What capabilities and size?
Be sure to purchase a gateway that can accommodate your system's current call load as well as planned future growth. Which leads us to the next question...
4. How Many Simultaneous VoIP Calls Can the Gateway Handle?
It's important to select a product that can keep pace with the network call load. Purchase a gateway that can handle a call load that's a useful margin greater than existing traffic levels.
5. How Many FXO Ports Are Provided?
These are required to interface the gatway to incoming PSTN lines (analogue or digital) make sure that any gateway you're planning to buy at has enough FXO ports for existing and future requirements.
6. What bandwidth is available from my ISP
The key task required of a gateway is to convert analog voice signal into the digital format that allows it to be transferred through a VOIP network. Different rates of compression (codecs) can be applied but more compression reduces voice quality. For maximum control over bandwidth usage you need equpment that automatically controls quality of service (QoS).
You want as much flexibility and features as possible. There's also always the possibility of standards appearing over time, meaning your gateway will have to keep pace with the new technology. So choose a product that is possible to upgrade.
Different products offer different levels of support
7. Is the Gateway Compatible With My existing Hardware?
If the VoIP gateway needs to interoperate with a number of existing technologies, then you shoud research carefully its compatibility.
8. What Type of Support is offered?
Beyond the gateway itself, you need to discover the level of support the vendor offers. How long is the basic warranty? Does the vendor provide adequate support? Is on-site support available? Can the provider login remotely and fix small issues? What is the cost of their service?
These are all key things to know before you make your final purchase decision.
Selecting the right gateway for your business can be a confusing and time consuming process. But asking the right questions will ensure that you get the product and support you need at a price you can afford.