# Technical Information

## Supported Codecs

- OPUS/48000/2
- G722/8000
- PCMU/8000
- PCMA/8000
- G729/8000
- GSM/8000
- telephone-event (for DTMF transport)

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## IP addresses and RTP ports

- 46.19.208.0/21 (46.19.208.0 - 46.19.215.254) - for incoming and outgoing traffic.
- 46.19.210.69 - for sending [deliveries](../Delivery-methods/delivery-methods.html#ps3-delivery-methods).
- RTP port range - 16384-32767

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## DTMF Transport Methods

DTMF signaling is supported as follows:

- Telephone-event: [RFC2833](https://tools.ietf.org/html/rfc2833)
- SIP INFO: [draft-kaplan-dispatch-info-dtmf-package-00](https://tools.ietf.org/html/draft-kaplan-dispatch-info-dtmf-package-00)

  > - application/dtmf-relay
  > - application/dtmf

Note

By default, RFC 2833 is enabled.

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## Protocols

- SIP over UDP (User Datagram Protocol)
- SIP over TCP (Transmission Control Protocol)
- t.38 for fax transmission (to email)
- SIP over TLS (Transport Layer Security)
- SIP over WSS (WebSocket Secure)

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## Audio file formats

Supported audio files for uploading to Audio Files (file size is
limited to 14 MB)

- .mp3
- .m4a
- .wav
- .flac
- .ogg

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## Call Recording File Specifications

- File format .mp3
- Bit rate 16 kbps
- Sample rate 8 kHZ

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## Time Zone

phone.systems(TM) is using UTC offsets and daylight-saving rules issued by
IANA

- IANA Time Zone database - <https://www.iana.org/time-zones>
  (<https://en.wikipedia.org/wiki/Tz_database>)
- Default timezone is GMT (+0)

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