FreeRadius and PostgreSQL configuration question

[NECTIS NetVoice Sales]

Dear Gurus!

We try to install Freeradius with PostgreSQL but got question

We expect about 100 concurrent calls and our switch sent 3 requests to
radius: Authorization, accounting start and accounting stop or update.
How much max_connections we should configure in a postgresql.conf file?

Normally at the same time we will get about 1-30 calls. But we are not sure 
How much it will be. 

Is there some other or special recommendation for correct configuring of
PostgreSQL and FreeRadius.

Please, who had installed and configured that, send this information ASAP,
it's really necessary.

Best regards,