ST-ACR1M Audio Controlled Relay
The audio controlled relay unit shall be an RDL ST-ACR1M. The unit shall provide a balanced mic-level audio input. Valid audio at the input shall cause the internal DPDT relay to be active. The unit shall provide an open-collector output, which shall be labeled SLAVE. The open-collector output shall be active when the relay is active. The SLAVE terminal shall also serve as an input; connection of the slave terminal to ground shall over-ride the audio detector and shall place the relay in the active condition.  The unit shall delay releasing the relay contacts following loss of a valid audio input.  Adjustments shall be provided for audio input sensitivity and to set the release delay period.  An indicator shall be provided for adjustment of the audio sensitivity.

The input shall be electronic balanced bridging with a nominal input impedance of 10 kOhms and shall be fully compatible with either an unbalanced or balanced mic-level audio source. A continuously adjustable multi-turn trimming control shall be provided to set the sensitivity of a level detector to qualify a valid audio input. The sensitivity control shall allow adjustment for input levels from -60 dBu to -20 dBu.  The detection circuit shall switch the relay to the active condition within 25 ms of qualifying a valid audio input signal.

The relay switching circuit shall be equipped with an open-collector output capable of sinking at least 25 mA. The relay contacts available at the terminal block shall be 2 Form C rated to switch 60 W at a current of up to 2 A. The relay shall be a sealed high-reliability type specified to provide more than 1,000,000 operations.

Upon loss of a valid audio input, the unit shall delay the release of the relay contacts and open-collector output. A continuously adjustable multi-turn trimming control shall be provided to set the duration of the release delay timer from 0.5 seconds to 5 seconds nominal.  Upon completion of the release delay interval, the unit shall wait 250 ms to respond to the next valid audio input signal. The unit shall be rated for use as both an audio detector and/or as a silence sensor.

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 50 mA with a 20 mA load connection between the open-collector slave output terminal and the power supply. 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-ACR1M.