Having some spare time on my hands, a bridge and some telephone headsets, I measured the inductance and impedance at 1000 cycles single headset type R2A 1.49h and Z=10k single headset type R15 1.85h and Z=10k ;------------- whole earphone, ie 2 headsets type ANB-H-1 0.2h and Z=3.3k I believe all of the above headsets are military Phil