Electrically fired displays bring a few variables into the equation. By firing each device electrically, you have complete control over exactly when each will fire, as opposed to a hand fired display in which delays in the quickmatch or fusing can cause unwanted gaps in your show. In an electrically fired display, each device is rigged with an electric match.
Electric iginition increases the level of safety for the pyrotechnics crew discharding the display, being that they no longer need to be right up next to the fireworks they are setting off, as they would be during a manually fired display that uses torches or roadflares to ignite each match.
Electric matches use the concept of the incandescent light bulb. They consist of a tiny bridge wire which is coated with a pyrotechnic composition (which has a low ignition temperature). When a certain amount of electric current passes through the bridge wire, it heats up, quickly passing the ignition temperature of the pyrotechnic coating. The flame which the pyrotechnic coating produces ignites the device in question. In most cases, the e-match is stuck into a piece of quick match leading into a finale chain or directly into the lift charge of a shell. The electric matches ignite fairly instantaneously due to the large amount of current that most pyrotechnic firing systems (see below) put out. The "instantaneous" nature of electric matches allows for very precise firing of shells and related devices.
***Electric matches are the most sensitive item pyrotechnicians deal with. They are both shock and friction sensitive and need to be handled with care to avoid setting them off during handling.
Firing systems come in different sizes and with different capabilities. Firing systems typically operate off of 24 volts, but can range anywhere from 9 volts to 250 volts. The number of shots you can shoot from each system can vary as well.