An interface protocol for patient monitoring systems includes a Dual Serial Bus (DSB) interface. The DSB interface includes a first serial protocol that is USB, Firewire, or Ethernet protocol and a second serial protocol that is a low power serial (LPS) protocol. DSB interfaces provide for communication between DSB Hosts and DSB Devices and allow for the transfer of operating and battery charging power from DSB Host to DSB Device. In addition, the DSB host contains a switched Auxiliary Voltage Supply (AVS) which can provide up to 15 W of power to DSB devices for battery charging or other high power needs. The DSB interface eliminates the need for multiple cables for different parameter sensing devices as there is only one type of connector and, accordingly, reduces the risk of damage caused by inadvertently plugging a parameter sensing device into the wrong receptacle.