Technical Specifications
Need to know what's under the hood? Here's a detailed look at the technical capabilities of your phone system - from supported audio formats to network requirements. Whether you're setting up integrations or just curious about the system's capabilities, you'll find all the technical details here.
Audio Codecs​
The system supports multiple audio codecs to ensure optimal call quality and compatibility:
| Codec | Sample Rate |
|---|---|
| OPUS | 48000/2 |
| G722 | 8000 |
| PCMU | 8000 |
| PCMA | 8000 |
| G729 | 8000 |
| GSM | 8000 |
The system also supports telephone-event for DTMF transport, ensuring reliable touch-tone functionality during calls.
DTMF Support & Third-Party Integration​
DTMF Tone Recognition​
The FlyNumber phone system fully supports DTMF (Dual-Tone Multi-Frequency) signaling through the telephone-event codec, which is essential for:
- Navigating IVR menus
- Entering PIN codes or passwords
- Confirming selections with button presses
- Responding to third-party service prompts
Third-Party Platform Requirements​
When integrating with third-party services that require DTMF input (like call verification systems or interactive platforms), ensure the following:
| Requirement | Description |
|---|---|
| Telephone-Event Codec | Must be enabled in the third-party's SDP (Session Description Protocol) signaling |
| Codec Negotiation | Third-party platform must properly negotiate DTMF codec during call setup |
| DTMF Transport Method | RFC 2833/RFC 4733 compliant telephone-event payload |
Troubleshooting DTMF Issues​
If button presses aren't working when receiving calls from third-party services:
- Verify the issue: Test DTMF tones with other services to confirm FlyNumber is sending tones correctly
- Contact third-party support: Provide them with this technical information:
- They need to add/enable the telephone-event codec in their SDP signaling
- The codec is required for DTMF tone recognition
- The issue must be fixed from their call origination point
- Common symptoms:
- Pressing buttons doesn't trigger expected actions
- IVR prompts repeat as if no input was received
- Call connects but button commands are ignored
If a third-party service cannot detect your button presses, the issue is typically on their end, not with your FlyNumber. The FlyNumber system correctly sends DTMF tones when the receiving platform is properly configured.
Network Configuration​
IP Ranges ​
The system uses the following IP range for incoming and outgoing traffic:
46.19.208.0/21 (46.19.208.0 - 46.19.215.254)
RTP Ports​
Media traffic uses ports in the following range:
16384-32767
When configuring firewalls or security settings, ensure these IP ranges and ports are properly allowed for optimal system performance.
Supported Protocols​
The system supports multiple protocols for flexible integration:
- SIP over UDP (User Datagram Protocol)
- SIP over TCP (Transmission Control Protocol)
- SIP over TLS (Transport Layer Security)
- Uses default port 5061 when TLS is enabled
- Provides encrypted signaling for secure communications
- SIP over WSS (WebSocket Secure) - Phone System App Only
- Used exclusively by the phone system app for secure web-based communications
- Establishes encrypted TLS connections for app communications
- Enables secure real-time communication through web browsers and mobile apps
- T.38 for fax transmission (to email)
Audio File Specifications​
Supported Upload Formats​
The following audio file formats can be uploaded to the Media Center:
- .mp3
- .m4a
- .wav
- .flac
- .ogg
Maximum file size for audio uploads is 14 MB
Call Recording Specifications​
Call recordings are generated with the following specifications:
- File format: .mp3
- Bit rate: 16 kbps
- Sample rate: 8 kHZ
Call recordings are approximately 7MB per hour. Consider this when configuring email delivery methods, as email servers may have file size limitations.
Time Zone Management​
The system implements the industry-standard IANA Time Zone database for precise time management:
- Uses UTC offsets and daylight-saving rules from IANA
- Default timezone is GMT (+0)
- Supports all IANA timezone definitions
- Automatically handles daylight saving transitions
For more information about IANA timezones, visit:
System Requirements​
Mobile App​
The phone system app is available for:
- iOS devices
- Android devices
- Windows computers
- macOS computers
Web Interface​
The phone system panel (HTML 5 based) works best with:
- Modern web browsers (Chrome, Firefox, Safari, Edge)
- Minimum screen resolution: 900x600 pixels
- JavaScript enabled
- Cookies enabled
Security Features​
The system includes several security measures:
-
SIP Security
- TLS support for encrypted signaling
- SRTP support for encrypted media
- IP-based authentication options
- Strong password requirements
-
Web Interface
- HTTPS encryption
- Session-based authentication
- Role-based access control
- Activity logging
Encrypted protocols (TLS, SRTP) are disabled by default. Contact support to enable these features for your account.
Integration Capabilities​
The system supports various integration methods:
-
Cloud Delivery Methods
- AWS
- Azure
- MinIO
- Google Drive
- Dropbox
- OneDrive
-
File Transfer
- FTP
- SFTP
- Email attachments
-
External Systems
- SIP trunking
- External SIP URIs
- PSTN routing (Phone number forwarding)
- Interlink connections
For optimal performance when integrating with external systems, ensure all required ports and protocols are properly configured in your network security settings.
Global Calling Capabilities​
The system provides advanced global calling features with localized rate structures:
Rate Categories​
- Local Calling: Use FlyNumber to call within the same country at local rates
- EU Calling: Special rates for calls within European Economic Area (EEA)
- Standard International: Competitive rates for other international destinations
Call Forwarding Specifics​
- EU rates apply for EU-originated calls forwarded to EU numbers
- Standard rates apply for other international forwarding scenarios
- Local rates not applicable to forwarded calls
When using a UK FlyNumber to call UK numbers, you pay local UK rates. Note that US calls have consistent rates regardless of which FlyNumber you're using, making it an exception to the local rate structure.
Some countries may have specific rate structures that differ from the standard local/EU/international categories. For current pricing details, see our phone system billing guide or check the phone system rates.