Frequently Asked Questions (FAQ)
Internal Extensions and Call Limits
Are internal extensions limited by the license?
No. There is no limit on the number of internal extensions. The only limitation is hardware capacity.
What does the license limitation “maximum number of concurrent calls” mean?
The limitation applies only to outgoing calls to the voice service provider. Incoming and internal calls within the system remain unlimited.
Devices and Integration
What devices can be connected to the PBX?
Any device compatible with the SIP protocol: phones, analog/ISDN converters, GSM gateways, or door entry systems. Contact us for help with device selection.
Can custom features be developed?
Yes. Our complete development team works in-house, which allows flexible response to client requirements.
Operational Questions
Does the system work during a power outage?
Yes, with basic UPS backup. However, it is necessary to ensure power supply for the phones and a working data connection.
Can I reuse analog phones from an old PBX?
Yes, through analog FXS converters. Digital phones from proprietary systems cannot be reused due to manufacturer-specific protocols.
Do I need a PBX for each branch office?
No. A single central PBX is sufficient for all branch offices. Remote phones register to the central system with optional encryption or a VPN tunnel.
Technical Protocols
| Protocol | Description |
|---|---|
| SIP | Session Initiation Protocol — the standard signaling protocol for VoIP (RFC 3261). Text-based, flexible, and the most widely used. |
| SDP | Session Description Protocol — defines parameters of streamed media, such as audio codec selection. |
| H.323 | An older set of standards for audio/video communication, gradually being replaced by the simpler SIP. |
| RTP | Real Time Transport Protocol for audio/video transmission with optional quality feedback via RTCP. |
| T.38 | A protocol for fax transmission over Ethernet networks, converting fax into image format for network delivery. |
SIP Status Codes
1xx — Informational
| Code | Meaning |
|---|---|
| 100 | Trying |
| 180 | Ringing |
| 181 | Call Forwarding |
| 182 | Queued |
| 183 | Session Progress |
2xx — Success
| Code | Meaning |
|---|---|
| 200 | OK |
| 202 | Accepted |
3xx — Redirection
| Code | Meaning |
|---|---|
| 300 | Multiple Choices |
| 301 | Moved Permanently |
| 302 | Moved Temporarily |
| 305 | Use Proxy |
| 380 | Alternative Service |
4xx — Client Errors
| Code | Meaning |
|---|---|
| 400 | Bad Request |
| 401 | Unauthorized |
| 403 | Forbidden |
| 404 | Not Found |
| 408 | Request Timeout |
| 480 | Temporarily Unavailable |
| 486 | Busy Here |
| 487 | Request Terminated |
| 488 | Not Acceptable Here |
5xx — Server Errors
| Code | Meaning |
|---|---|
| 500 | Server Internal Error |
| 501 | Not Implemented |
| 502 | Bad Gateway |
| 503 | Service Unavailable |
6xx — Global Failures
| Code | Meaning |
|---|---|
| 600 | Busy Everywhere |
| 603 | Decline |
| 604 | Does Not Exist Anywhere |
| 606 | Not Acceptable |