H837ASPB/H838ASPB/H839ASPB is a 64-channel POTS service board that provides POTS access service.
The Huawei ASPB board supports the following functions:
64 channels of POTS access services
All ports support polarity reversal configurations for a single port or all ports in batches. The feeder voltage is -48 V
Circuit test and loop line test
Loop connectivity test
Port protection
Board power-off for energy conservation
BORSCHT for analog user circuits

Please note:
H837ASPB has the same functions as H838ASPB; therefore, H837ASPB can substitute for H838ASPB.
Compared with H837ASPB/H838ASPB, H839ASPB supports a new function: direct current-isolated (DC-I) grounding.

The basic working principle of the Huawei ASPB board is as follows:
The protection module protects and isolates the board from lightning strikes.
The subscriber-line interface module provides access to 64 channels of POTS services.
The codec module encodes and decodes voice signals and converts analog signals into digital signals.
The MCU module processes the upper-layer protocol messages between the board and the control board and manages user ports of the board.
The power module supplies power to other function modules of the board.
The clock module provides the working clock for other function modules of the board.