APM2.8 Specifications:
Compared with APM 2.8 without a welded electronic compass on the mainboard, the board has no onboard compass.
System: complete open-source autopilot system
APM2.8 Features:
1. It allows the user to turn any fixed, rotary wing, or multirotor vehicle (even cars and boats) into a fully autonomous vehicle; capable of performing programmed GPS missions with waypoints.
2. This revision of the board has no onboard compass, which is designed for vehicles (especially multicopters and rovers) where the compass should be placed as far from power and motor sources as possible to avoid magnetic interference. (On fixed-wing aircraft, it is often easier to mount APM far enough away from the motors and ESCs to avoid magnetic interference, so this is not as critical, but APM 2.8 gives more flexibility in that positioning and is a good choice for them, too). This is designed to be used with the 3DR uBlox GPS with Compass, so that the GPS/Compass unit can be mounted further from noise sources than APM itself.
3. APM 2.8 requires a GPS unit and external compass for full autonomy. Choose your compass from the options menu on the right.

915Mhz Radio Telemetry Specifications:
Antenna connectors: RP-SMA connector
Output Power: 100mW (20dBm), adjustable between 1-20dBm
Sensitivity: -117dBm sensitivity
Interface: standard TTL UART
Connection status: LED indicators

GPS Specifications:
With fast satellite searching speed and high precision
Power supply cable: the default APM style
Compass: 6M
Terminal outgoing lines: compatible with APM serial port and I2C port

OSD Specifications:
Operating voltage: 5V-12V
Application: DIY flight control quadcopter
OSD Features:
1. Perfect combination of ATmega328 and MAX7456.
2. Flight control OS functions   
3. Supports MAVLink protocol.
4. Uses MAVLink OSD.
5. Supports APM2.6 and APM2.5.2 flight models.

Power Module Specifications:
Max input voltage: 25V
Max current sensing: 90A
Voltage and current measurement configured for 5V ADC
Switching regulator outputs 5.3V and 2.25A maximum
6-pos DF13 cable plugs directly to APM 2.6's 'PM' connector
Package size: 15 * 11 * 6cm / 5.9 * 4.3 * 2.4in