For the two big bubble chambers BEBC and Garga-melle (GGM), detectors for external muon identification had been requested. Choice was given to multiwire proportional chambers behind additional iron absorbers. 71 chamber modules (each 1 x 3 m2) with two independent anode wire planes and one cathode strip plane have been built. To record the particle hits without deadtime during the spill length of 3 ms the development of a readout system quite different from standard systems was necessary. The chambers, the electronics and the performance of both systems will be described.