xringd(8) on Linux
The text 5a1a21560d81, as Debian 1.3 (Bo), Debian 1.2 (Rex), Debian 1.1 (Buzz) shipped it.
The Linux extended modem ring server
Flags it lists
-
-? -
-a -
-c -
-d -
-h -
-i -
-l -
-m -
-n -
-t