From: http://success.ringcentral.com/articles/RC_Knowledge_Article/How-to-Get-the-SIP-Configuration-needed-for-Manual-Provisioning-2013?retURL

From: http://success.ringcentral.com/articles/RC_Knowledge_Article/4543?retURL=%2Fapex%2FRCSupportPortalSearchNew%26type%3DFAQ%26id%3DkA280000000GsvoCAC%26Title%3DUpdated+SIP+Servers+for+manually+provisioned+IP+phones

SIP Domain sip.rengcentral.com:5060
Outbound Proxy: sip20.ringcentral.com:5090
New Servers
sip10.ringcentral.com or 199.255.120.176
sip20.ringcentral.com or 199.255.120.177

To configure your device to connect to the RingCentral service, you will need to program it with the following information.
The steps for programming will vary from device to device, so please check with your device's manufacturer for specific instructions.
Field			Value
SIP Domain		sip.ringcentral.com:5060
Outbound Proxy		sip10.ringcentral.com:5090
User Name		15555551212
Password		1234567
Authorization ID	1234567