DBMS_ALERT from trigger does not work, why?

Hi,

I try to use the DBMS_ALERT package from a trigger and it will not work though I can user DBMS_ALERT from the command line (see examples below)! So it's not as easy as "run catproc" or "grant execute on SYS.DBMS_ALERT to ME".
I never had trouble with this before, but I am not installing on my own server but on someone else's (i.e. I have not much rights to go roaming in the system and would anyway not know where to look). Any suggestions?
Please reply by e-mail, too (it's faster!). TIA,         Almut

SQL> create table t1 (t1 number(3));

Table created.

SQL> create or replace trigger tt1
  2 after insert or update on t1
  3 begin
  4 dbms_alert.signal('hello', 'msg');   5 end;
  6 /
create or replace trigger tt1
*
ERROR at line 1:

ORA-06550: line 4, column 3:
PLS-00201: identifier 'SYS.DBMS_ALERT' must be declared
ORA-06550: line 4, column 3:

Oracle7 Server Release 7.2.3.0.0 - Production Release PL/SQL Release 2.2.3.0.0 - Production
CORE Version 3.4.3.0.0 - Production
TNS for HPUX: Version 2.2.3.0.0 - Production NLSRTL Version 3.1.4.6.0 - Production

-- 
Almut Herzog
SECTRA-Imtec AB                     e-mail: al-her_at_sectra.se
Teknikringen 2                      voice:  ++46 13 235221
583 30 Linkoping                    fax:    ++46 13 212185
SWEDEN