The lower circuit board accomplishes many tasks. Firstly and most importantly, it houses the main part of the marker's electroincs, encompassing the microcontroller and all related components. This means it's the circuit that is "programmed" to operate the marker. The lower board connects to the battery by a standard 9v battery connector.
Please note that there is no reverse voltage protection on the stock board. If the battery is plugged in backwards (negative to positive), the board may become damaged and need replacement.
The lower board also has an integrated lever-actuated microswitch, which is used to fire the marker by the trigger. The stock switch weight on the board is 25-g (this is the lowest available return weight).
The lower board is held in place by the two roll pins that hold the trigger microswitch (above) in place. The board is removeable by removing the two roll pins, using a hammer with metal punch, nail, another roll pin, or whatever other tool you can find. Personally, I use a pair of needlenose pliers to remove the pins.
Be wary of scratches to the frame, since this spot is only slightly covered by the grip panels.
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Here is a video to demonstrate board pin removal. Push out the board pins, pull them out the other side, remove the board and wiring harness.
(right click, save as)
Care must be taken when reassembling the body with the frame. The wire harness connecting each board must remain out of the way of any parts. Please refer to the Powerswitch & Wire Harness page in the Related Links section.
Board Adjustment:
One of the other most important features of the lower board is that it is the platform by which the marker's electronic settings (dwell, ROF, etc) are adjusted. For instructions on how to adjust the board's settings, follow the link at the bottom of the page to the adjusting and maintaining section of the site.
Aftermarket Boards:
The function of an aftermarket board in a Nerve is the same as in a Shocker. For a list of aftermarket boards please check the Shocker's lower circuit board page in the Related Links seciton.
Stock Board Technical Specifications: 
Here are some technical specifications for the stock Smart Parts lower board (Shocker/Nerve).
· The only part of the board that functions off 9-v is the powerswitch, which is carried to the upper board through the wire harness.
· Lower board regulates straight battery voltage to 7-v using a Linear Technology LT1962 voltage reg, which supplies 300-mA to the solenoid through the wire harness, and also to the rest of the lower board.
· Most of the board components run from 5-v, regulated through a National Semiconductors LP2981 voltage reg. This includes the input switches (pull-up type), board speaker, and microcontroller.
· The microcontroller is an Atmel ATmega8L AVR. The board programming is locked and the circuit is designed to prevent cold booting.
· Trigger microswitch is a 25 gram leverswitch, Omron part number D2F-FL.
· Power and programming switches are subminiature side-actuated tactile switches, ITT CANNON part number KSS321G (7mmx3.5mmx1.6mm).
· Wire harness connector is a 10-point, shrouded, side-entry type JST eSH series header, JST part number BM10B-SRSS-TB. Wire harness is 32 AWG wire connected between two protrousion-less housings, JST part number SHR-10V-S-B.
Lower board pictures:
· Reverse-engineered circuit schematic:
Specifications for the upper circuit board can be found on the upper board page in the Related Links section.
Overview:
· The lower board controls the main functions of the marker, and is the method by which the marker is electronically adjusted.
· Shocker runs off a standard 9v battery.
· The lower board is held in place using two small roll pins, placed through the trigger microswitch.
Related Links:
· Adjusting the electronics settings (Shocker SFT lower board page)
· Aftermarket lower boards (Shocker SFT lower board page)
· Upper circuit board
· Powerswitch actuator & wire harness
· Flipped microswitch mod
· Microswitch tensioner mod