This is a simple and cheap astable multivibrator. The o/p waveform is governed by the R2 and C1 (time constant = 0.69R2C1) and the low time By R3 and C2 (time constant = 0.69R3C2).
The o/p at both collectors is out of phase.
If r2=r3=r(say) and c1=c2=c(say) then o/p signal frequency is given by f=1/(1.38RC)
