Simple circuit - radio transmitter 4 button key pad for toy car

[Grossel]

Hi forum.

Have this project I intended to do like 10 years ago, now I finally had found time for it. So I have this little radio controller for a toy car. Unfortunately, all but the PCB remains, and I don't remember (nor worked out) the correct DC voltage - I can only guess 9V by now.
Also the TR3 transistor have an unreadable surface (scraped off?) so I can only guess it's the same type transistors as the rest.

The layout is being made out by deciding I want to have the antenna symbol at right and the key pad at left. Also, my daily work for many years now has not involved analog electronic/radio circuits at all - in fact, it's like 25yrs ago I had this topic at school, so forgive me if I'm decayed when it comes to analog rf circuit design.

Some key points of possible wrongs and incompleteness on this:

• VCC voltage not worked out yet (from memory long back, I believe it's 9V)
• TR2 should probably being re-arranged to right side of TR3 (for easy reading - maybe).
• TR3 is actually unknown due to surface tear down/scraped away, but diode test indicates same polarity of BJT.
• Inductance of inductors not worked out (all components still on the PCB).

The thing I want to discuss is the working of TR2 and TR3. I assume those make up an oscillator, but I think I need some help identify what type of oscillator and what components makes up that oscillator - I'll use this as base for improvement of the shematic (re-ordering) so it get more easy to see the oscillator component group apart from the others.

 

[augustinetez]

Ignoring the bits associated with the switches, TR2 & 3 form an astable multivibrator.

The extra resistors appear to change the pulse width of the multivibrator which is how most RC gear worked back then.