That all depends on what type of headsetconnector the Telex uses and what type of Clearcom system you have. If its a standard 4 pin headset, it will probably work with most Clearcom packs. This is provided the pack or the headset isn't a stereo headphone setup, because that doesn't run on a four pin but a six pin system for the headset.
This probably should've been posted in the sound forum fyi.
Yup, you can. There is a jumper in some telex packs that you have to move to stop some call light funkiness, but all in all it should work even without the jumper move. Look at the manual of your specific pack, it should mention it.
I know my high school and college have both used Telex headsets with ClearCom beltpacks (i've heard the Telex ones are cheaper). They all work fine together.
Telex makes beltpacks that are for use on a clearcom type system, and they make beltpacks that are specic to the original telex type system. They are not compatible. If using the wrong type of telex pack on a clearcom system, there will be a reduced volume and the mic will be very low and distorted.
The fact that Telex owns clearcom and RTS companies, indicates that they will make beltpacks or interfaces to go between the different systems. Production intercom is of the clercom type system.