Philips BV300 Pulsera DFI Combo PB4 Board 4522 127 0281Philips BV300 Pulsera DFI Combo PB4 Board 4522 127 0281 The PB4 board is one of the logic control cards within the DFI combo module of the Philips BV300 Pulsera system. It manages charge circuitry and interlock monitoring for defibrillation therapy, interfacing with the main CPU and power boards. Key Specifications Board Number: 4522 127 0281 Function: Defibrillator charge control and safety interlocks Connectors: Boardtoboard edge connector;