IBM A50 User Manual page 107

Attention Switzerland User:
If your Swisscom phone line does not have Taxsignal switched OFF, modem
function may be impaired. The impairment may be resolved by a filter with
the following specifications:
Telekom PTT SCR-BE
Taximpulssperrfilter-12kHz
PTT Art. 444.112.7
Bakom 93.0291.Z.N
91
Appendix C. Manual modem commands