The APO-15 connection board is designed as a space-saving alternative for new control systems. The connection options and functions largely correspond to those of the APO-14; however, the APO-15 is not backward-compatible with previous APO versions.

Despite its compact dimensions of 210 × 78 mm, the APO-15 has been expanded to include three freely programmable relays, a direct connection option for the MS Digifon, and additional terminals for emergency lighting changeover. Furthermore, eight freely programmable I/O are now available on bus module 51. Instead of individual bus modules, a pluggable 4-channel bus module of type ION32 is used.

The connections for the pulse generator and copying block have been omitted in favor of the reduced dimensions.