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Documentation Index

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A 4-digit identifier prepended to outbound calls to differentiate multiple SIP connections sharing the same IP address.

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Dial string format

[tech_prefix][destination_number]
Example: Tech prefix 1234 + destination +18005678912 = 123418005678912

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Use cases

  • Multiple SIP connections from the same IP address
  • Granular call routing and billing per connection
  • Traffic stream separation

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Configuration

PATCH /v2/ip_connections/ 
{
  "inbound": {
    "sip_subdomain_receive_settings": "from_anyone"
  },
  "outbound": {
    "tech_prefix_enabled": true
  }
}
Tech prefix value is assigned by Telnyx and visible in the connection settings.

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Phone system setup

The PBX or SIP client must prepend the tech prefix to all outbound calls on the trunk.

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Authentication behavior

ConditionResult
Correct tech prefix includedCall authenticated
Missing or incorrect prefix407 Proxy Authentication Required

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Alternative authentication methods

For connections sharing an IP address:
MethodDescription
Tech prefix4-digit prepended identifier
IP authentication tokenToken-based validation
P-Charge-Info headerSIP header-based routing