[TYPO3-calendar] Use of a cal service

[Chris Müller]

Hi,

I want to get all events with a specified category via the cal service 
tx_cal_phpicalendar => cal_event_model in an own extension. I did this via

$service = t3lib_div::makeInstanceService('tx_cal_phpicalendar', 
'cal_event_model');

but I always get false instead of an service object. Can someone give me 
a hint how to get this working?

I also read the relevant part in the cal and core documentation but had 
no enligtenment.

Regards,
Chris.