Direct Coupled Discrete Astable Multivibrator
This flip-flop circuit is a free running/astable multivibrator one, with bases and collector of both emitter biased transistor are directly coupled to each other. Switching action is supported by means of capacitor in each emitter circuit. This configuration produce a triangle waves at emitters. Since neither transistor can remain permanently cut off, then a free running oscillation will be generated. We can use single 0.1 uF capacitor between emitters in place of C1 and C2.
[Circuit’s schematic diagram source: Chang, Two New Direct-Coupled Astable Multivibrators, IEEE Proceedings, March 1973, p 390-391.]