For sending SMS in the file includes/sms.php is defined class Sms.
Sending SMS is connected and configured in the [Site settings] (/dokument/full-manual/sysmodules/config/) and is used in different modules.
void send (string $text, string $to) – Отправляет SMS.
Example:
// send SMS
Custom::inc('includes/sms.php');
Sms::send('The site has a new order #134.', '79999999999');