diff --git a/application/config/config.sample.php b/application/config/config.sample.php
index 40d31c7c6..40ae48586 100644
--- a/application/config/config.sample.php
+++ b/application/config/config.sample.php
@@ -14,7 +14,14 @@ defined('BASEPATH') OR exit('No direct script access allowed');
 
 $config['app_name'] = 'Wavelog';
 $config['directory'] = 'logbook';
-$config['callbook'] = 'hamqth'; // Options are hamqth, qrz, qrzcq or qrzru
+/*
+| Options are hamqth, qrz, qrzcq or qrzru
+| For a single callbook configure just one value as string. Example:
+| $config['callbook'] = 'hamqth';
+| This can also be set to an array of callbooks to search sequentially until a match is found. Example:
+| $config['callbook'] = ['qrz', 'hamqth'];
+ */
+$config['callbook'] = 'hamqth';
 
 $config['datadir'] = null; // default to install directory