I've always known not all Contax flashes work on all Contax bodies but I've never been sure which combinations work and which don't. I decided to do a little research and some tests. Here's the results.
I think the best way to understand the combinations is to split the various cameras and flashes into three groups thus:
Group 1: Early models
This includes the 139, 137 (MA and MD) and RTSII bodies (see note 1) and TLA20, TLA30 and RTF540 flashes (see note 2).
Group 2: Later models
This includes all SLR bodies from the 159 onwards and TLA280, TLA360 and TLA480 flashes.
Group 3: G models
This includes the G1 and G2 bodies and TLA140 and TLA200 flashes.
Group 1 used two additional contacts on the hot shoe. One was for the flash to indicate to the camera it was ready (Ready signal) and the other was for the camera to stop the flash when sufficient exposure had been given (TTL Control signal).
Group 2 also used two additional contacts but now the Ready and TTL Control signals were combined onto one contact while the second contact was used as an Auxilliary Sync contact for flashes that could support second curtain sync. The Auxilliary Sync contact also retained the function of TTL Control so retaining backward compatibility with older flash units.
Group 3 is essentially the same as group 2 except neither of the flashes have second curtain sync capability so only have one additional contact. The cameras do have second curtain sync capability so have two.
So to summarise: Groups 2 and 3 cameras are compatible with all TLA flashes (see note 5). Group 1 cameras are only compatible with Group 1 flashes. In theory, Group 1 cameras can use Groups 2 and 3 flashes but only in manual mode, however, when trying it myself, the flash made a rather disconcerting noise after each flash suggesting some connection between the additional contacts was not ideal. I wouldn't recommend this.
1. The original RTS had no built-in flash control so is not included.
2. There was an earlier version of the RTF540 which did not have TLA capability.
3. I found the TLA280 would not physically fit onto a 139 body due to the additional contacts catching the edge of the hot shoe. If the contacts were manually depressed, it could be made to fit. Maybe this was a deliberate design choice to stop them being used together.
4. The Aria, RX, RX2 and AX bodies have 2 more additional contacts, so 5 contacts in total. The 2 extra contacts are clock and data signals to pass extra information to the flash. As far as I know, only the TLA360 has this capability.
5. I don't have examples of every camera and flash so this is based on a combination of information I've read such as camera operator manuals, tests on the combination of bodies and flashes I do have and some assumptions.