GSM prepaid
 

how can i tell if a prepaid calling card is offering GSM or VOIP services?

i know travelsim uses GSM, what about
1) easyroam,
2) Globalsimcard.co.uk
3) gosim.com

where can i get a list of provider going prepaid International GSM calling card?

I'm not sure if this is a bit of a misnomer, or you're blurring categories

The names you mention are all SIM cards, thus GSM, and use prepaid credit

Calling cards is usually a name for separate services using a prepaid balance to make other calls, for instance by VoIP or via access numbers which may be called from either landlines or mobiles. But when using access numbers, the calling card is using the host network but is independent of it.

You can find details of global SIM cards either on a link at the top of here, in this and other forums, or by doing internet searches for global or roaming SIMs. Calling cards - there seem to be hundreds or thousands. VoIP providers, definitely several thousand.

Some prepaid uses VOIP, of which the delivery of communications is over over IP networks such as the Internet or other packet-switched networks, or you can call it
Internet telephony. Company that uses this are like Truphone, Jajah, in fact most of the prepaid players in the market, are still susceptible to IP network latency, which can result into low quality voice or lag between caller and receiver as they speaks.

Whereas players like Travelsim uses PSTN (traditional public switched telephone network), of which the quality is unquestionable (so its a challenge for this catergory of player to lower the cost)

anyone knows who else is the true PSTN GSM player in the market, as my company are tired of using VOIP of which our salesperson overseas sometimes has got problem communicating with customers and us in the office and sometime that even happen when we do conference using those VOIP across borders.

that is why we want to subscribe to a very good quality prepaid for our salespeople and also to use it in the office for conferencing, esp when companies like TravelSim has free incoming for so many countries.

I have tried travelsim, its good so far, but the estonian number to call out is not cheap if you are not in europe, though the incoming is good if you are in europe. Therefore we want to have a some proper "Apple to Apple" comparison before we commit to a company wide change to the other GSM PSTN based prepaid providers.

Comments, Folks!

I don't understand why you blur different types of products together, or how you expect a SIM card to solve your conferenve call issues.

Whilst global SIMs are hybrids using a number of suppliers to make each work, I understand that they mainly use reputable national and international pstn carriers to connect the calls, rather than VoIP. Two of those you mention in the first post certainly do so, while I don't know for the third but it's the same as Travelsim from Estonia that you mentioned.

Truphone and Jajah are pure VoIP-serivces, which have nothing to do with GSM or mobile telephony and so won't provide a SIM card, allthough you may use these services from a handset.
However even those providers offering GSM services through a SIM card don't necessarily use conventional PSTN-technology. Especially for roaming a lot of international routing is performed over IP due to cost savings and so sometimes even circuit-switched GSM-technology may suffer from the weaknesses of the packet-switched Internet Protocol.

Don't think there is really that much difference in voip or through pstn. It's all about compression and even pstn will use compression sometimes.

I use my voipcallback to the sim or calls are forwared by voip to the sim. I don't have any quality issues. the gsm codec itself is not the highest quality but good enough so I really don't see any point if a call to or from a gsm is made through voip or not.

What about user experience? which gives good PSTN voice quality and low outgoing rates?