phantom voltage
The term phantom power is used for the supply of condenser microphones, but also for a supply mode with Power over Ethernet( PoE). Namely for the supply of communication components in Ethernet networks.
Phantom powering for condenser micro
phones When powering condenser microphones, phantom power is a polarization voltage used to bias the condenser microphones. In these microphones, the condenser diaphragm must be biased so that it does not vibrate through its resting state during sound pickup, causing distortion. For this reason, the diaphragm is placed at the potential of the phantom voltage, which is between the moving diaphragm and the fixed electrode. The phantom voltage is specified in DIN 45 596 and IEC 60268-15 and can have a value of 48 V, 24 V or 12V, which is fed through resistors of 6.8 kilo-ohms, 1.2 kilo-ohms and 680 ohms, respectively. When feeding, the same potential is applied to both wires of the microphone's balanced conductors. The purpose of this is to allow dynamic microphones to be connected without being affected by the phantom power. In practice, the 48 V is connected to contacts 2 and 3 of the XLR connector, and the ground is connected to pin 1. Since no voltage can be measured between pin 2 and pin 3, this has led to the name phantom power. The 48 V of phantom power (P48) has historical reasons, which lie in the tube amplifiers used in the past. This voltage is provided by mixing consoles or camera recorders. The phantom power has replaced the former tonearm power supply, where the 12 V DC voltage is applied directly to the signal lines. This technology was originally standardized under DIN 45595.Phantom powering in Power over Ethernet
In Power over Ethernet (PoE), phantom powering is one of several operating modes used to supply power to Powered Devices( PD) from Power Sourcing Equipments( PSE). In phantom powering, the voltage is fed from the PSE unit via the RJ45 connectors and the TP cables to the connected end devices, the Powered Devices (PD), via the lines over which the data is also transmitted. It thus overlaps the data signals. With 100Base- TX, the phantom power is routed via pins 1/2 as well as 3/6; with 1000Base-T, which is Gigabit Ethernet, all eight pins are used. In the second operating mode, spare pair powering, the power is supplied via the free pins 4/5 and 7/8. Phantom powering is used when all wire pairs are used for data transmission.
