| 1/00 | Details of selecting apparatus or arrangements |
| 1/02 | Details of selecting apparatus or arrangements Constructional details |
| 1/04 | Details of selecting apparatus or arrangements Constructional details Frames or mounting racks for selector switches; Accessories therefor, e.g. frame cover |
| 1/06 | Details of selecting apparatus or arrangements Constructional details Cable ducts or mountings specially adapted for exchange installations |
| 1/08 | Details of selecting apparatus or arrangements Constructional details Frames or mounting racks for relays; Accessories therefor |
| 1/10 | Details of selecting apparatus or arrangements Constructional details Exchange station construction |
| 1/12 | Details of selecting apparatus or arrangements Constructional details Arrangements of multiple bars with or without pivotable frames |
| 1/14 | Details of selecting apparatus or arrangements Constructional details Distribution frames |
| 1/16 | Details of selecting apparatus or arrangements Constructional details Wiring arrangements for selector switches or relays in frames |
| 1/18 | Details of selecting apparatus or arrangements Electrical details |
| 1/20 | Details of selecting apparatus or arrangements Electrical details Testing circuits or apparatus; Circuits or apparatus for detecting, indicating, or signalling faults or troubles |
| 1/22 | Details of selecting apparatus or arrangements Electrical details Testing circuits or apparatus; Circuits or apparatus for detecting, indicating, or signalling faults or troubles Automatic arrangements |
| 1/24 | Details of selecting apparatus or arrangements Electrical details Testing circuits or apparatus; Circuits or apparatus for detecting, indicating, or signalling faults or troubles Automatic arrangements for connection devices |
| 1/26 | Details of selecting apparatus or arrangements Electrical details Testing circuits or apparatus; Circuits or apparatus for detecting, indicating, or signalling faults or troubles Automatic arrangements for signalling trouble in unoccupied sub-exchanges |
| 1/28 | Details of selecting apparatus or arrangements Electrical details Current-supply circuits or arrangements for selection equipment at exchanges |
| 1/30 | Details of selecting apparatus or arrangements Electrical details Signalling arrangements; Manipulation of signalling currents (multiplex systems providing for calling or supervisory signals H04J 1/14, H04J 3/12
) |
| 1/32 | Details of selecting apparatus or arrangements Electrical details Signalling arrangements; Manipulation of signalling currents (multiplex systems providing for calling or supervisory signals H04J 1/14, H04J 3/12
) using trains of dc pulses (H04Q 1/39 takes precedence) |
| 1/34 | Details of selecting apparatus or arrangements Electrical details Signalling arrangements; Manipulation of signalling currents (multiplex systems providing for calling or supervisory signals H04J 1/14, H04J 3/12
) using trains of dc pulses (H04Q 1/39 takes precedence) Impulse regenerators with mechanical or other non-electrical marking arrangements |
| 1/36 | Details of selecting apparatus or arrangements Electrical details Signalling arrangements; Manipulation of signalling currents (multiplex systems providing for calling or supervisory signals H04J 1/14, H04J 3/12
) using trains of dc pulses (H04Q 1/39 takes precedence) Pulse-correcting arrangements, e.g. for reducing effects due to interference |
| 1/38 | Details of selecting apparatus or arrangements Electrical details Signalling arrangements; Manipulation of signalling currents (multiplex systems providing for calling or supervisory signals H04J 1/14, H04J 3/12
) using combinations of direct currents of different amplitudes or polarities over line conductors or combination of line conductors |