Okay, well, did some looking into the FM 24-24 edition I have, which is the 1994 edition, there are several types/designations of shelter installations:
Switches:
TTC - Automatic Telephone Central Office (TTC = Transportable (Ground), Telephone (Wire), Communications (2-way))
TYC - Automatic Message Switch (TYC = (Transportable (Ground), Data Processing, Communications (2-way))
Teletypewriter:
MSC - Telegraph Terminal (MSC = Ground Mobile, Special or Combination, Communications (2-way))
TSC - Telegraph Terminal (TSC = Transportable (Ground), Special or Combination, Communications (2-way))
Multichannel:
TCC - Telephone Terminal (TCC - Transportable (Ground), Carrier (Electronic Wave or Signal), Communications (2-way))
TRC - Radio Terminal/Repeater Set (TRC - Transportable (Ground), Radio, Communications (2-way))
Multichannel Satellite Communications Terminals:
FSC - Satellite Communications Terminal (FSC = Fixed Ground, Special or Combination, Communications (2-way))
GSC - Satellite Communications Terminal (GSC = General Ground Use, Special or Combination, Communications (2-way))
MSC - Satellite Communications Terminal (MSC = Ground Mobile, Special or Combination, Communications (2-way))
MSQ - Satellite Communications Control (MSQ = Ground Mobile, Special or Combination, Special or Combination)
TSC - Satellite Communications Terminal (TSC = Transportable (Ground), Special or Combination, Communications (2-way))
High Frequency Radio:
GRC - Radio Teletypewriter Set (General Ground Use, Radio, Communications (2-way))
VSC - Radio Teletypewriter Set (Vehicle (Ground), Special or Combination, Communications (2-way))
Communications and Operations Centers:
GSQ - Message Center (GSQ = General Ground Use, Special or Combination, Special or Combination)
MSC - Communications Operations Center (MSC = Ground Mobile, Special or Combination, Communications (2-way))
TYQ - Communications System Control Element (TYQ = Transportable (Ground), Data Processing, Special or Combination)
TSC - Communications Patching Center (TSC = Transportable (Ground), Special or Combination, Communications (2-way))
TSQ - Communications Technical Control Center (TSQ = Transportable (Ground), Special or Combination, Special or Combination)
SO, all that being worded out and analyzed, to answer my own question, there are several designations that could potentially be used for a radio installation in a military shelter (S-250, S-280, S-144, S-788, etc.)