• double
  actual time (ckt->CKTtime)
• double*
  delta time (ckt->CKTdelta)
• double
  old delta time (olddelta)
• int
  identification number of calling ngspice shared lib
• int
  location of call for synchronization in dctran.c
• void*
  return pointer received from caller

Ask for new delta time depending on synchronization requirements. See 19.6.1 for an explanation.