Parallel usage of old relay interlocking systems in many locations together with microprocessor-based interlock-ing systems in modernised stations of the same railway operator places high requirements on new track section occupancy control devices. As microprocessor-based signalling systems with much smaller equipment dimensions re-place the respective relay systems, the new track section occupancy control device should also be able to replace as many old section occupancy control devices as possible with less equipment and less power dissipation, without reduction of safety and reliability. During line modernisation, many railway operators decide to use axle counters instead of track circuits for track section occupancy control, both in stations and on open lines, in view of their many advantages such as immunity to track resistance variations, greater section length, lower power dissipation per section, elimination of track insulation joints and track inductors as well as related traction power loss, etc. Since almost every railway operator in the European Union today uses a lot of different signalling systems with different dates of manufacture, the new axle counter should easily fit into both the relay and microprocessor-based interlocking or automatic block system, and should be able to replace both track circuits and old axle counters, if needed. It should also be able to control the occupancy of the long section between stations either via copper cables or fibre optics. The new axle counter should also accommodate various ways of resetting the section manually to the basic state. The BO23 multi-section axle counter was developed to satisfy all the above-mentioned requirements and to provide a safe detection and counting of axles and section occupancy control with minimal maintenance costs and minimal equipment dimensions for a number of track sections.