The EFT209-T21 is a Resistor-Capacitor (RC) Filtering Network from Teledyne. It is a two-pole, two-section, low-pass filter with a cutoff frequency of 21 MHz. It is used to filter out noise in high-frequency signals. The EFT 209-T21 is designed for communications and signal processing applications, and is typically used in audio signal filtering, signal isolation, signal routing, and impedance matching circuits.