Function of Bhavanga - Bhavanga-citta has only one function

When an object contacts one of the five senses the stream of bhavanga-citta is interrupted and there is a sense-impression. However, there cannot be a sense-impression immediately. When sound, for example, impinges on the ear -sense, there is not hearing immediately. There are still some bhavanga-cittas

arising and falling away before the pañca-dvārāvajjana-citta (five-sense-door-

adverting-consciousness) adverts to the sound through the ear-door and

hearing arises. The bhavanga-cittas do not perform the function of adverting

to the sound which contacts the ear-sense, they do not experience the sound.

They have their own function which is keeping the continuity in a lifespan,

and they experience their own object which is the same as the object of the

patisandhi-citta. Although the bhavanga-citta does not experience the sound

which contacts the ear-sense, it can be affected, 'disturbed' by it and then the

stream of bhavanga-cittas will be interrupted and sound will be experienced

by cittas which arise in the ear-door process.

 

When a rūpa impinges on one of the senses bhavanga-cittas can be affected

by it. First there is one moment of bhavanga-citta arising and falling away

which is denoted by the name 'atīta-bhavanga' or 'past bhavanga'. Then it

is succeeded by the 'bhavanga calana' or 'vibrating bhavanga'. It is called

vibrating since it is disturbed by the object, although it does not experience it.

The last bhavanga-citta of the stream of bhavanga-cittas and before the

pañca-dvārāvajjana-citta adverts to the object is the bhavangupaccheda or

'arrest bhavanga'.

  The different names which denote these bhavanga-cittas do not represent different functions; bhavanga-cittas have as their only function to keep the continuity in the life of a being. The different names point only to the fact that these bhavanga-cittas are the last ones when the stream is interrupted and a new object is experienced by a process of cittas. When the sense-door process is over, the stream of bhavanga-cittas is resumed, so that the series of cittas succeeding one another in our life is not interrupted.
The object which impinged on one of the senses is then experienced through the mind-door. In between the sense-door process and the mind-door process, however, there are bhavanga-cittas.  When the cittas of the mind- door process have fallen  away, the stream of bhavanga-cittas is resumed.