The S3-TBO unit contains a comfortable talkback system with a build-in condensor mic, a Listen system with several inputs, a test tone oscillator, and 4 switches for user functions.

An additional stereo source selector with 8 stereo inputs makes it possible to expand the capacity of the control source selector.

The Talkback Section
The Talkback system has two inputs. Input one is a microphone amplifier for the integrated electret condenser microphone. This omni-directional low noise mic offers are high quality talkback signal, independend of the position of the operator. The second input can be used for an external mic or a line level source as well. The zero ohm input of the external talkback amplifier can be adapted to accept any input level by two external resistors. Phantom power for the external input can be activated by jumper. The maximum gain is 60 dB. The internal microphone can be disabled by jumper. There is an enable switch for the external input. In addition this input can be enabled by a 24 V remote control signal. The internal and external talkback signals have separate control pots and can be mixed. There are two balanced external talkback outputs that are available on the connector panel. Separate switches activate these outputs. The TB-Group and TB-Aux-Switch feeds talkback to the talkback aux bus and the talkback group bus. Switches on the aux master amplifiers and the group master amplifiers make it possible to enable and disable talkback for the particular master. The Talkback Studio switch enables the talkback inputs of the headphone and speaker sections of the playback modules STU3. If talkback is switched to the particular output or not is determined by the TB Off switch of the section. The level control takes places with the talkback pots of the headphone and studio section.

The Listen system rmakes it possible to feed an additional microphone in the studio to the console's PFL system. In addition to the Listen Mic Input, there is a line input to connect the console's listen and talkback system to an external talkback system. Of course, this input can be used for any purpose, that requires a PFL function without the need that this signal is connected to an input channel. Both the mic input and the line input are electronically balanced. The maximum gain of the mic input is 60 dB. Phantom power can be enabled for this input by an internal jumper. The listen line input accepts levels of up to + 20 dBu.
Separate level pots for mic and line make it possible to summ both the signals. An ON switch per input enables the particular input. This function can be remote controlled by a DC voltage. There are several possibilities to automate the listen function and to assign it to one of the user switches.

The Listen Lock switch disables all listen functions. The balanced listen output is always active unless the Lock function disables the entire listen system. In addition, listen control can be switched to the PFL Bus and to the Autodim bus by two switches.

The Oscillator is sinewave test tone generator that can be switched to 5 fixed frequencies (40 Hz, 100 Hz, 1 kHz, 10 kHz and 15 kHz) by a stepper switch. The output level is normally calibrated to + 6 dBu (1.55 V) but it can be adjusted to any required level by a trimpot. If the LEVEL POT ON switch is pressed, the output level is controlled by a pot in the range from off to + 20 dBu. A balanced, separate output is available on the connector panel. In addition, the oscialltor can be internally assinged to the Aux Bus and the Group & PGM bus. The OSC switches in the aux master and group master section determine if the particular output is enabled for the osciallator signal or not.

The 4 User switches are connected to a 25 -Pin D-Sub connector on the rearpanel of the console. These switches are fully floating and not internally connected. Per switch a NC contact, a NO contact and the LED is available. Usually, the switches are non latching versions. Latching version are available as well as engraved caps in several differnt colors.

The Stereo Source Selector
8 additional stereo sources can be connected to the select switch block that is part of the module. The section uses a mechanical switch array with mutual release that is electrically interlocked. It is passive and switches the balanced stereo lines. The output of the selector is available on one of the stereo switches of the surround control room unit by external wiring on the connector panel. The selector can be used as an input select of a stereo channel alternatively.

The Talkback Switches

5 non latching switches activate talkback to the external talkback output, the Aux talkback bus, the Group talkback bus and the studio talkback separately. Latching versions of the switches can be installed on request. A remote input for the talkback studio switch is available on the connector panel.