To add to the previous answer, the initial investigation period does not include ‘time outs’ which include:
a) Time taken to take the accused to the nearest police station or location with investigation facilities.
b) Time taken to arrange, wait for and/or communicate with a criminal lawyer, relative, friend, guardian, embassy official, interpreter or doctor.
c) Time taken to arrange and receive medical treatment.
d) Time reasonably required to arrange and undertake an identification parade (police ‘line-up’).
e) Time taken for the accused to rest, have refreshments, or go to the toilet.
f) Time taken for the accused to recover from the effects of alcohol and/or drugs.
g) Time reasonably required to wait for the arrival of police officers or people with special skills necessary for the investigation.
The total amount of ‘time outs’ cannot exceed 2 hours. If it exceeds 2 hours, then the additional period of time (for example, 30 mins if the period totalled 2 hours, 30 mins) will be counted towards the 4-hour investigation period.
Source: http://www.legalaid.nsw.gov.au/publications/factsheets-and-resources/police-powers