src/app/code/community/StackExchange/RequiredTelephone/etc/config.xml
<?xml version="1.0"?>
<config>
<modules>
<StackExchange_RequiredTelephone>
<version>1.0.0</version>
</StackExchange_RequiredTelephone>
</modules>
<global>
<models>
<stackexchange_required_telephone>
<class>StackExchange_RequiredTelephone_Model</class>
</stackexchange_required_telephone>
</models>
<events>
<customer_address_validation_after>
<observers>
<stackexchange_required_telephone>
<class>stackexchange_required_telephone/observer</class>
<method>validateAddress</method>
</stackexchange_required_telephone>
</observers>
</customer_address_validation_after>
</events>
<resources>
<stackexchange_required_telephone_setup>
<setup>
<module>StackExchange_RequiredTelephone</module>
</setup>
</stackexchange_required_telephone_setup>
</resources>
</global>
</config>