SimpleSLICFilter

SimpleSLIC Filter

A pair of active filters and basic switching circuitry that mounts to the underside of a SimpleSLIC.

With SimpleSLIC mounted:

The audio input path features an RC high pass filter and a Sallen-Key low pass filter with a slight gain. The audio output path features an RC high pass filter partially constructed with the 100nF in line with the SimpleSLIC's audio output pin, followed by a Sallen-Key low pass filter, and an additional high-pass filter that introduces a DC bias into the signal.

After filtering, audio paths are fed to a CD4066 bidirectional switch, which switches the audio channels onto two rails.

• When pin 3 (EO) is driven high, the Audio output is switched onto pin 9 (O) and audio input is switched onto pin 11 (R)
• When pin 5 (ER) is driven high, the Audio output is switched onto pin 11 (R) and audio input is switched onto pin 9 (O)

Pin 3 effectively puts the device into "Originate" mode, and pin 5 puts the device into "Receive" mode (or "Answer" mode, if you prefer). Do not drive both pins high at the same time.

By connecting two devices' O pins and R pins together, then driving one device's EO pin high, and the other device's ER pin high, a "call" between the two devices is established.

Licensing

This project is licensed under the terms of CERN-OHL-S, Version 2. A copy of the license can be found in the LICENSE file included in this repository.

This repository contains files from third-party sources. Such files are located in the Libraries/3rdparty directory. Licensing information for these files has been included with those files, when such information was provided by the vendor.