Despite the extensive knowledge of the characteristics of the coherent radio emission, the mechanism is not understood. The high-energy radiation is incoherent and may be related to the flux of relativistic electrons and positrons in a current sheet at the boundary of the magnetosphere. The radio emission from the polar cap is at lower frequency at larger radii, as the magnetic field lines diverge. The emission may be affected by propagation through the polar cap; refraction along the magnetic field lines may increase the apparent pulse width at lower frequencies.

Advances in observing techniques, the commissioning of new radio telescopes and the prospect of the Square Kilometre Array are opening new fields of pulsar research. The 55 years since the discovery of pulsars have revealed a rich and evolving population and shown how precise timing can transform our understanding of neutron star structure, binary system dynamics, stellar populations and the interstellar medium, and have opened new prospects in general relativity physics. X-ray and gamma-ray telescopes, and Cerenkov shower arrays, are extending observations over the whole electromagnetic spectrum.

The majority of millisecond pulsars are in binary systems with white dwarfs or other neutron stars. Precision timing yields remarkably accurate orbital parameters and their evolution. Binary systems provide tests of relativistic effects including energy loss by gravitational waves.

Describes the diverse techniques used in telescopes for the very wide range of the electromagnetic spectrum covered by pulsar observations. Conventional telescopes for the visible range can be used with suitable high time resolution, while only the lowest energy x-rays can be focussed to form images. Higher x-ray and gamma-ray energies require individual photons to be detected and tracked. The highest energy gamma-rays are detected in Cerenkov air-shower arrays. In contrast to the photon detection of all high-energy radiation, radio telescopes and receivers treat radiation as waves with measurable amplitude and phase, allowing multiple beams to be formed in large phased arrays of radio telescopes.

The discovery of millisecond pulsars revealed an evolutionary sequence from normal binary stars to x-ray binaries and the millisecond binary pulsars. The companions of binary millisecond pulsars include other neutron stars and white dwarfs with various masses.

The ionised interstellar medium is ideally accessible to radio pulsar research, both on large scales through frequency dispersion and on small scales through scattering and random refraction of radio waves. The theory is presented both geometrically and as wave diffraction. Observations reveal structure on a wide range of scales, including the effects of discrete structures. Interstellar scattering also lengthens radio pulses.

The radiation from most pulsars has a high degree of linear polarisation, allowing measurements of Faraday rotation. Such radio observations of polarisation provide detailed measurements of the interstellar magnetic field along the line of sight to a pulsar, including the fields along the spiral arms and the large-scale field outside the plane of the Galaxy. Pulsars can probe the magnitude and direction of the galactic magnetic field.

Many of the masses of pulsars in binary systems are known to high accuracy from their dynamics, while the masses of solitary pulsars are difficult to obtain. Radii are available from x-ray luminosity where this is known to be thermal. This chapter assembles the known measurements of mass and radius for all neutron stars.

A brief history of the discoveries and their subsequent development gives an introduction to the research topics dealt with in later chapters: pulsar searches, precision timing, positions and identifications, millisecond pulsars, binary systems, neutron star structure, general relativity, emission mechanisms, fast radio bursts, interstellar medium.

Pulsar radio emission is variable on many time scales, from nanosecond structure in single pulses to intermittency on timescales of many years. Isolated single pulses may be intense individual pulses from a regular sequence, or individual fast radio bursts. The excitation of radio emission varies both in its location and its timing.