[root@localhost ~]# isql -v asterisk-connector
+---------------------------------------+
| Connected!                            |
|                                       |
| sql-statement                         |
| help [tablename]                      |
| quit                                  |
|                                       |
+---------------------------------------+
SQL> select 1 from rdb$database
+------------+
| CONSTANT   |
+------------+
| 1          |
+------------+
SQLRowCount returns 1
1 rows fetched
SQL>