The Siemens 6ES7960-1AB04-0XA0 is a SIMATIC S7-400H synchronization module V4, designed for use with routed fiber-optic cable up to 10 km between the two CPUs in a redundant S7-400H system. It draws a maximum of 250 mA from the backplane and dissipates a typical 1.3 W, which is modest enough that thermal buildup in a densely packed rack is not a concern.
It snaps into the S7-400 rack alongside the CPU and I/O slices — the 25 mm width is standard for one-wide S7-400 modules, so it occupies a single slot without crowding adjacent cards.
It is the V4 revision of the synchronization module, which is the current version for new S7-400H builds and for replacing earlier V3 modules in existing redundant systems.