The U-13R from TOA Electronics is an input module for 900 series equipment. It accepts unbalanced line-level signals from devices such as CD players, tape decks, and AM/FM tuners. It has dual RCA jacks for device connection. It also has gain control, high and low cut pass filters, and responds to mute bus activation.
In the Box
Toa Electronics U-13R - Unbalanced Line Input Module with High/Low Cut Filters and Mute-Receive for 900 Series (Dual RCA)