Fader Resource

Fader Resources are used in the AlphaCom System for providing clickfree audio switching between sources in group audio features.

Usage

One fader resource is used when one of the following functions are activated:

• Groupcall (switch between gong tone and microphone, fade in/out when m-key is pressed/released.
• Simplex conference

In a multimodule, one fader is needed in each participant module.

A fader is used along with two timeslots. The audio source is connected to the source timeslot. The fader loops the audio to the distribution timeslot. All listeners listen on the distribution timeslot. When switching sources, the fader fades out the source audio, and keep feeding the distribution timeslot during the switch. The listeners are not involved in the switch.

Realization

We use the otherwise unused SBI subchannel 0 of the Audio Scanners as Fader Resource. (All SBI Channel has a fader function on subchannel 0). The SBI subchannel is set in Loopback mode when used as Fader Resource.

Two Fader resources are found on each subscriber line board:

• ASLT
• ATLB
• On the ATLB12 board there are 4 fader resources.

From AMC version 10.31: The AMC-IP board provides 12 fader resources, by using unused "SBI channels" realized by the FPGA. These faders limits the audio to 7 kHz bandwidth. The AMC SW will use SBI based faders if available, and fall back to FPGA faders if no SBI faders are available.