# Building AWS Lambda functions for the Amazon Chime SDK PSTN audio service
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The topics in this section explain how to build the AWS Lambda functions used by your PSTN audio service. 

**Topics**
+ [Understanding telephony events for Amazon Chime SDK PSTN audio service](pstn-invocations.md)
+ [Understanding Amazon Chime SDK PSTN audio service actions](about-actions.md)
+ [Learn about the telephony events that invoke AWS Lambda functions for the Amazon Chime SDK PSTN audio service](invoking-Lambda.md)
+ [Responding to invocations with action lists using the Amazon Chime SDK PSTN audio service](invoke-on-call-leg.md)
+ [Supported actions for the Amazon Chime SDK PSTN audio service](specify-actions.md)
+ [Using SIP headers in the Amazon Chime SDK PTSN audio service](sip-headers.md)
+ [Using call detail records in the Amazon Chime SDK PTSN audio service](attributes.md)
+ [Understanding timeouts and retries for the Amazon Chime SDK PTSN audio service](timeouts.md)
+ [Debugging and troubleshooting the Amazon Chime SDK PTSN audio service](debug-pstn.md)
+ [Understanding VoiceFocus for the Amazon Chime SDK PTSN audio service](voice-focus.md)
+ [Amazon Chime SDK PSTN audio service glossary](chm-dg-glossary.md)