How to configure the Obihai OBi110 for the United Kingdom PSTN

The OBi110, as with most ATAs, comes configured for the US. For those of us on the other side of the pond, in the UK, it’s always a challenge to get ATAs to work. Here are the required settings for the OBi110 in the UK. They’ve been acquired collectively from a few sources but have been proven to work for inbound and outbound calls. Anything not mentioned should be left with the Default checkbox ticked.

Physical Interfaces -> PHONE Port:

  • Impedance: 370+(620||310 nF)
  • CallerIDMethod: FSK(V.23)
  • CallerIDTrigger: After Polarity Reversal
  • HookFlashTimeMin: 150

Physical Interfaces -> LINE Port:

  • RingDelay: 0 (don’t worry, caller ID still works if it’s enabled on your line)
  • RingProfile: B (the default B profile seems to work well in the UK)
  • CPCTimeThreshold: 90
  • DetectPolarityReversal: Unticked
  • SilenceTimeThreshold: 30
  • DisconnectTonePattern: 400-30;2
  • ACImpedance: 370+(620||310 nF)
  • OnHookSpeed: 3 ms (ETSI)
  • CurrentLimitingEnable: Ticked
  • CallerIDDetectMethod: FSK(V.23)
  • RingFrequencyMin: 10
  • RingThreshold: 13.50-16.50
  • RingIndicationDelayTime: 0
  • RingTimeout: 128

Tone Settings -> Tone Profile A:

  • Dial Tone: 350-18,440-18;20
  • Ringback Tone: 400-18,450-18;20;(.4+.2,.4+2)
  • Busy Tone: 400-18;20;(.375+.375)
  • Reorder Tone: 400-18;20


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  1. How to set up the Obihai OBi110 as a PSTN gateway - […] If you are in the UK, you should read my other post about configuring the PHONE/LINE (FXS/FXO) settings to…

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