ST-VP1 Voice-Over / Paging Module
The audio ducking unit shall be an RDL ST-VP1. The unit shall provide two line-level inputs and one line-level output. One input shall be designated for music and one input shall be designated for voice. Two trigger inputs shall be provided, one to fade the music down, the other to shut off the music input. The unit shall detect a ground potential at the fade terminal and automatically fade down the volume of the music for the duration that the fade terminal is held at ground. Upon release of the fade terminal the unit shall fade up the volume of the music. The unit shall detect a ground potential at the cut terminal and automatically switch off the music for the duration that the cut terminal is held at ground. Upon release of the cut terminal the unit shall turn on the music input. The voice input shall be active when audio is detected and shall otherwise remain fully muted. All audio switching functions shall be clickless, “soft” audio solid-state switching with no relays or electro-mechanical switching devices in the audio path.

Each input shall be electronic balanced bridging with an input impedance no less than 20 kOhms and shall be fully compatible with either an unbalanced or balanced audio source. The normal input signal level shall be +4 dBu.

Two continuously adjustable multi-turn trimming controls shall be provided. One trimmer shall be provided to set the attenuation of the music while the fade terminal is triggered. One trimmer shall be provided to set the rate of fade applied to the music source when the fade terminal is triggered or released.

The unit shall provide a music input audio frequency response of at least 10 Hz to 20 kHz (± 0.25 dB) with total harmonic distortion plus noise of <0.01% (20 Hz to 20 kHz) and a noise floor exceeding 85 dB below the normal rated output level. The fade depth of the music input shall be adjustable from 3 dB to 40 dB.  The fade rate of the music input shall be adjustable from 0.3 to 1.3 seconds for 20 dB attenuation. The unit shall provide a voice input audio frequency response of 30 Hz to 20 kHz (± 0.25 dB) with total harmonic distortion plus noise of <0.01% (20 Hz to 20 kHz) and an attenuation exceeding 80 dB when muted. Nominal input to output gain shall be unity.

The unit shall provide a line-level balanced audio output at a nominal rated output level of +4 dBu with an output impedance of 150 O. The output circuit shall be configured to produce an unbalanced output of proper phase between the positive output leg and ground. 

The unit shall be constructed in an electrically non-conductive, thermally conductive enclosure. Internal circuitry shall be protected from moisture and vibration using a thermally conductive compound that permanently secures the circuitry within the enclosure.

The face of the unit shall provide graphical labels identifying wiring connections and operating controls. Indicators and controls shall be oriented toward the front edge of the unit.

Connection to external wiring shall be provided using a fixed terminal block on the edge of the unit. The terminal block shall accept wiring gauges from 14 to 22 and shall include a positive electrically conductive mechanism to prevent wire abrasion by the terminal screws.

The unit shall measure 3” (7.6 cm) x 1.6” (4 cm) x 0.7” (1.7 cm) and be compatible with all RDL STICK-ON mounting accessories. The unit shall be supplied with a two part re-closable polypropylene fastener system equipped with a rubber adhesive that bonds to low surface energy materials.

Power requirements shall be 24 Vdc ground-referenced with a maximum current not exceeding 45 mA. The unit shall utilize an external power supply. The unit shall be engineered, assembled and tested in the U.S.A. and be specified for continuous duty in professional installed systems. The unit shall be specified for operation in an ambient temperature between 0 and 55 degrees C. The unit shall comply with relevant EMC requirements and shall bear the CE marking.

The unit shall be an RDL ST-VP1.