The processes entailed in the attainments can be described in a series:
The Past Moment of the life continuum, PM. (Atîta-bhavaàga)
Vibration of the Continuum, VC. (Bhavaàga Calana)
When the irritation appears at the mind door, the life continuum vibrates twice and the passive stream of consciousness, APS, become arrested (VC-APS).
Then the mind door (MD) diverts the stream of consciousness towards the patibhaga nimitta, (PM-VC-PSA-MD-CS)
Arrest of the Passive Stream of consciousness, APS. (Bhavaàga Upaccheda)
Mind Door, MD (Manodvâra)
Concentration Sign, CS (patibhaga nimitta)
This is a conscious sign which is observed and as a result the concentration can be conidered as progressing satisfactorily or not.
It is stated in the Visuddhi Magga that the variety of forms and objects visualized is due to differences in 'sañña,' perception, of the individuals concerned.
Commencing from the time of this CS, the samadhi which is then developed is called "Upacara-samadhi."
Then calmness arises which permits Access Concentration, upacara samâdhi javana.
it acts as a bridge harmonizing the lower consciousness with the higher consciousness. Then consciousness cuts the sense desire to form the more exhalted state.
Access to Concentration, AC. (upacara samâdhi javana.)
This is followed by,
Conformity of the Concentration, CC. (Anuloma)
Change to Attainment of a higher level, CA. (Gotrabhû)
and the ATTAINMENTS emerge in series. (PM-VC-PSA-MD-CS-AC-CC-CA-ATT)
Attainments, ATT (Jhâna)
The resultant four consciousnesses are known as upacara samâdhi javana.
The four levels of Rûpa Jhâna begin, attain and dwell at the first attainment (Jhâna) which is coincident with vitakka, vicâra, pîti and sukha which arise from tranquility (viveka).