Difference in Triax connector types

Question

What is the difference between TRB and TRC? What do they stand for? what are they referring to exactly? While we are on this subject, what are TRT, TTM, TRX, TRS? I have scoured the internet with no information at all. Everyone in this industry seems to know what these terms/types stand for and not a single datasheet bothers to explain it. I assumed it is different connections to the conductors, but doesn't seem like it. Can anyone give me a guide?

I have decyphered most other terms. 2/3 lug/slot (how many pegs are there), coax/twinax/triax, the not very obvious male/female (referring only to the innermost conductor, not the outer shell), but for the life of me, I cannot figure out this TRB, TRS thing (along with the other types). What does it even refer to?

I cannot just buy them and see them for myself, they are 1- very expensive, and 2- the difference may not be observable from the outside, especially when I don't even know what am I looking at. With very expensive equipment (B1500, completely custom probes (long-story, don't ask)), I can't just buy anything and cross my fingers. If I don't fry the equipment, at would at least not know what am I really measuring.

For context: I am looking for adapters and possibly coax cables. We will probably have to connect to BNC at some point before the DUT (I know, I am losing some of Triax's functionality). The specifics of the setup are irrelevant.

Edit: upon further digging, I may have found something (this is all still speculation). These names seem to refer to the connector's shape and maybe size (like BNC, thanks @peter bennet).

• TRT/TTM: These seem to be threaded connectors with different sizes.
• TRB: seem to be BNC-like, can be with 3 or 2 lugs/slots. Some brochures claim it is only 3 though.
• TRC: seem to be BNC-like, can only be only 2 lugs/slots. I can find only one product (on both mouser and Digikey)

If someone's from the industry and can confirm, that would be nice.

Answer 1

All of these connector names, as far as I can tell, originate with Trompeter, a connector manufacturer that's now a subsidiary of Cinch Connectivity. If nothing else, their catalog seems to be the most useful source of information on these.

• TRB has the same outer dimensions as BNC and uses a bayonet lock, so it's the one you're likely most familiar with, since you say you use a B1500--these are the connectors used for the B1500 and B1505's SMUs (other than the HVSMU). TRB is available with 2, 3, or 4 bayonet lugs, as well as a push-on version that doesn't lock. Trompeter also calls this their "70 series".
• TRT is to TRB what TNC is to BNC. It's the same as TRB, but with a threaded locking system instead of bayonet; it has the same outer dimensions as TNC. Trompeter also calls this their "370 series".
• TRS and TTM are the triaxial equivalents of TPS (kind of a mini-BNC) and TCM (kind of a mini-TNC). They're basically the same as TRB and TRT, just shrunken a bit. Trompeter also calls these their 150 and 3150 series, respectively.
• TRC and TRN are, once again, the same thing, but larger this time; these have the same outer dimensions as C connectors (which are approximately the same size as N connectors). Trompeter calls them their 80 and 380 series, respectively.
• Series 450 and series 3450 connectors, which for some reason don't appear to have a three-letter name, seem to be even smaller than TRS and TTM, but I can't find any information on their dimensions. From the pictures I see, it seems to be about the size of micro-BNC.
• TWBNC and TWTNC are twinaxial connectors, not triaxial, but I figure they should get a mention too. They're the same size as BNC and TNC respectively, but have one pin and one socket inside instead of a pin and shields. Trompeter also calls them their 30 and 330 series.

Unfortunately, despite initially looking like it may be a TRN connector, it seems the B1500's HVSMU connector is something else. It's some kind of triax connector the size of an N connector, but with extended shields that make it incompatible with TRN. It may be something that was custom-made for HP/Agilent/Keysight and isn't available otherwise.

The other SMUs all seem to use standard TRB connectors, though.

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Most information sourced from Trompeter's catalog, with some additional help from this reseller's page. Some dimensional information (on both the triax connectors and, for comparisons, more familiar coax connectors) was sourced from Delta RF.