The model invokes one fBond and one eBond connector. The fBond connector is used at the inflow, i.e., where the flow variable is being computed, whereas the eBond connector is used at the outflow, i.e., where the effort variable is being computed. Thus, the causality stroke of this causal bond is at the inflow.
The model passes the effort and flow variables from the inflow to the outflow, and it sets the directional variable d to -1 at the inflow, and to +1 at the outflow.