Type 4 phaser

From Memory Alpha, the free Star Trek reference.

A type-4 phaser is a small ship-mounted phaser of a type generally used on shuttlecraft.

They were not normally installed on type-6 shuttlecraft during the year 2368 but could be fitted for special purposes. The phasers were located on the forward tips of the two warp nacelles. The Magellan, a shuttle from the USS Enterprise-D, was equipped with type-4 phaser emitters in order to chart the null space with a series of photon pulses in the J'naii star system. (TNG: "The Outcast")

Phaser technology
Tools: phaser bore • phaser drill
Weapons: Bajoran phaser • compression phaser rifle • Galor-class phaser bank • hand phaser • Kzinti phaser • particle phaser • phaser array • phaser bank • phaser cannon • phaser emitter • phaser type-1 • phaser type-2 • phaser type-3 • phaser type-4 • phaser type-8 • Regalian phaser rifle • regenerative phaser
Other: phaser coil • phaser range • phaser relay • phaser room • phaser sweep