DIAPI - Using JCO to link Activities and Service Calls

I am attempting to use the SAP B1 API to create and attach Activities to Service Calls.  I am using the Java connector (sapjco.jar).  There is virtually no help available online, other than the API documentation, and I can't locate the sample code that apparently comes as part of the install.

I can use the API to successfully create and update both Activities (IContacts) and Service Calls (IServiceCalls), but I don't know how to link them together. It would make sense if it was done like this

activity.setParentobjectId(call_id)

except this function does not exist.

I guess that maybe I need to use IRelationship, but the API doc says only this:

getRelationships(ICompany aCompany, java.lang.Integer lID)

          get Relationships object with specified ID, BoObjectTypes_oRelationships

Is this correct?  What should BoObjectTypes_oRelationships be?  Is anyone able to give me some guidance please, or at least a useful sample?

Thanks,