# Difference between extensions

**URL:** <https://community.asterisk.org/t/difference-between-extensions/16024>\
**Category:** Asterisk Support\
**Created:** [August 7, 2007, 10:30am UTC](https://community.asterisk.org/t/difference-between-extensions/16024 "2007-08-07T10:30:47Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![ironoxid](https://sea1.discourse-cdn.com/asterisk/user_avatar/community.asterisk.org/ironoxid/32/1044_2.png) [@ironoxid](https://community.asterisk.org/u/ironoxid)\
**Post date:** [August 7, 2007, 10:30am UTC](https://community.asterisk.org/t/difference-between-extensions/16024/1 "2007-08-07T10:30:47Z")

</div>

Hi,

Ii’ve red a lot on [voip-info.org](http://voip-info.org) but I don’t understand the difference between these two extensions

1. exten =\> 3,1,Dial(SIP/03397547XXX@swyx,20,rt)
2. exten =\> \_0.,1,Dial(SIP/${EXTEN}@swyx,20,rt)

What change?  
If i call by “3” anything goes very well.  
If i call direct by number 03397547XXX, my phone rings but when i answer I can’t hear anything ☹

Help me!

Thank you!

Giulio