Maybe your IT department goes out of its way to prevent you using Skype. Or perhaps you are using a borrowed computer and it wouldn't be polite to install an application.

But you really want to contact someone that you know will be available on Skype.

Now there's an answer.

If you have access to a SIP phone or softphone, you can use Gizmo5's OpenSky gateway to call Skype users.

This service can be used through upmarket VoIP systems from companies such as Cisco and Avaya, as well as Asterisk and other less expensive systems, and even Wi-Fi enabled Nokia mobile phones.

SIP addresses for Skype users are formed by appending @opensky.gizmo5.com to the Skype username.

Since alphanumeric entry may be awkward or even impossible on simple VoIP handsets, paying OpenSky customers are able to create all-numeric aliases via the Gizmo5 web site.

One problem is that the call won't go through unless the Skype user has selected "accept calls from anyone."

Calls of up to 5 minutes duration are free (though you may get bumped before the 5 minutes are up in busy periods), or you can make an unlimited number of longer (up to 2 hours) calls for $US20 per year for a single account.

Additional accounts can be purchased in blocks, eg 21-50 accounts cost $US800 per year. Network-wide licences are offered.