The 2257 from KR Electronics (A Division of NIC) is a Low Pass RF Filter with Frequency DC to 0.75 MHz, Stopband Frequency 900 KHz, 3 dB Cutoff Frequency 0.75 MHz, Lower Rejection 80 dB@900 KHz, Upper Rejection 3 dB@900 KHz. Tags: Plug In. More details for 2257 can be seen below.