EMP

An electromagnetic pulse generator (EMP) is an anti-electronics weapon that mimics the intense EM radiation emitted by a nuclear explosion. The resulting EM field couples with nearby electronics systems, producing massive, damaging electrical currents.

Just before the Cylon attack, "electric pulse generators" were being transported to Caprica from Battlestar Galactica on Colonial Heavy 798 (later Colonial One), presumably to place in a planetside museum or school as a historical artifact, or for re-use on another ship (Mini-Series).

As the destruction of the ship by a Cylon raid was imminent from nuclear missiles, Lee Adama activated the devices, giving the appearance that Colonial One had been destroyed by a nuclear blast. This attempt was successful, as the Cylons cut off the assault, the missiles were disabled, and Galactica's DRADIS confirmed the ship as destroyed. Colonial One's electronic systems seemed to be fully functional after the attack.

It is probable that these devices are standard equipment aboard ships such as battlestars, given Lee Adama's knowledge about the electric pulse generators. It is also probable that such devices were part of a battlestar's fighting tactics against Cylon attacks, since (at least in the first Cylon War, although not in the second), Cylons were purely mechanical and thus vulnerable to EMP attacks unless significantly shielded from the effect. Given that a non-military craft such as Colonial One recovered very shortly after the pulse, an EMP attack is temporary and does not permanently disable an attacker.

Pulses such as the one Adama initiated also cause human central nervous system electrical activity to be stunned, causing brief unconsciousness (Mini-Series). Given that the modern Cylon Raider is a bioorganic ship internally, it is possible that the Cylons designed the ship in this manner (among other reasons) to be much more resistant to EMP attacks.