  High-time-resolution X-ray observations of compact objects provide direct
access to strong field gravity, black hole masses and spins, and the equation
of state of ultra-dense matter. LOFT, the large observatory for X-ray timing,
is specifically designed to study the very rapid X-ray flux and spectral
variability that directly probe the motion of matter down to distances very
close to black holes and neutron stars. A 10 m^2-class instrument in
combination with good spectral resolution (<260 eV @ 6 keV) is required to
exploit the relevant diagnostics and holds the potential to revolutionise the
study of collapsed objects in our Galaxy and of the brightest supermassive
black holes in active galactic nuclei. LOFT will carry two main instruments: a
Large Area Detector (LAD), to be built at MSSL/UCL with the collaboration of
the Leicester Space Research Centre for the collimator) and a Wide Field
Monitor (WFM). The ground-breaking characteristic of the LAD (that will work in
the energy range 2-30 keV) is a mass per unit surface in the range of ~10
kg/m^2, enabling an effective area of ~10 m^2 (@10 keV) at a reasonable weight
and improving by a factor of ~20 over all predecessors. This will allow timing
measurements of unprecedented sensitivity, allowing the capability to measure
the mass and radius of neutron stars with ~5% accuracy, or to reveal blobs
orbiting close to the marginally stable orbit in active galactic nuclei. In
this contribution we summarise the characteristics of the LOFT instruments and
give an overview of the expectations for its capabilities.
