[Amps] TR switching

[kg7hf at comcast.net]

More of a curiousity question right now but, I notice in my trusty 3-500z amp, there is naturally a TR relay.  It's fairly hefty.  I see also that there is some band pass filtering, and that these are also contorlled by relays.  The band pass relays are much smaller than the TR relay.  Is this because the band relays are not going to be switching while "hot", or potentially "hot"?  I suspect that I couldn't use these smaller Zettler AZ820-2c-12DE type relays as a TR relay in anything with much more than a few watts?  

Thanks,
Paul (KG7HF)