This allows the administrator to use the vty interface to issue a silent
call to a given subscriber by using
"subscriber extension XXXX silent call start"
and stopping that silent call with
"subscriber extension XXXX silent call stop"
"Silent SMS" is a SMS that is delivered (and confirmed) but
not shown on the display of the phone. You can now send
such SMS by using
sms send silent extension 12345 text
or
sms send silent imsi 123451234512345 text