In about 2152, EM emitters were typically hand-held devices, each of which had a long handle. When several members of the Enterprise NX-01 crew were captured by a symbiotic lifeform, Malcolm Reed and a security team initially attempted to use these EM emitters to weaken the creature, as Doctor Phlox had determined that the creature was highly photosensitive.
Reed later jerry rigged some disc-shaped EM emitters that he programmed to set up a force field. These emitters each had a blue light that flashed on and off when they were ready for use, activated by a small button on the device, and could thereafter be operated by remote control. They were initially tested in the Armory aboard Enterprise, where their configuration was meanwhile displayed on a group of three screens. Four of these emitters were subsequently set up by Reed and another officer in a cargo bay where the creature was. Upon activating the jerry-rigged force field, Emitter B required slight adjustment, but Reed managed to correct it and the force field then held for as long as it was required. (ENT: "Vox Sola")
In 2153, Commander Tucker considered using portable EM emitters to fire sustained bursts of delta radiation at Xindi-Reptilian weapons in order to disable them, but Phlox warned him that the amount of delta radiation necessary to do that would also be extremely hazardous to humanoid life.
Subsequently, Tucker used four of Reed's force field emitters while testing a Xindi biorifle, believing they would contain the blast debris. However, they were ultimately not necessary, as the rifle wouldn't fire. (ENT: "The Shipment")