ST-IC1 Intercom Amplifier
The intercom amplifier shall be an RDL ST-IC1. The unit shall provide one balanced input, one amplified output capable of driving speaker loads of 4 O or greater, a single-turn gain trimmer and two muting control terminals of opposite actuation polarity.

The input shall be >600 O electronic balanced to accept microphone-level input signals from either a low-impedance loudspeaker or from a microphone. The input shall be fully compatible with either an unbalanced or balanced audio source. A single-turn trimming control shall be provided to set the microphone gain to a value between Off and 70 dB. The amplified output can produce 1 W RMS from an 8 O signal source of -60 dBu and from a 600 O signal source of -55 dBu.

A phantom terminal shall be provided to connect external phantom voltage which shall be filtered by the preamplifier to provide phantom voltage to the connected input source.

Two switching terminals shall be provided to mute the amplifier output.  One muting control terminal shall be activated when pulled to ground by a dry switch or relay contact or by an open collector capable of switching 2 mA; this terminal shall be internally pulled to +15 Vdc by the unit. The second muting control terminal shall be activated when pulled high to a voltage of 8 Vdc or greater; this terminal shall be internally pulled to ground by the unit. Activation of either or both muting control terminals shall instantly shut off the audio at the amplifier output. The off attenuation of the output amplifier, while muted, shall exceed 115 dB at 1 kHz.  Solid-state switching shall be used to mute the output amplifier.  Upon de-activation of both muting control terminals, the output amplifier shall return to normal output level within 15 ms.

The unit shall provide a frequency response tailored for voice-band intelligibility of 300 Hz to 4 kHz (± 2 dB) with total harmonic distortion plus noise <1% (1 kHz, 1 W, 50 dB gain) and a noise floor exceeding 75 dB below the normal rated output level with the amplifier un-muted and set to 60 dB gain. 

The unit shall provide an unbalanced mono amplified output at an output power of 1.5 W into a load impedance of 8 O. The unit shall include automatic shut-down circuitry to protect the unit from potential damage due to output over-current or overheating. The unit shall otherwise operate normally following application of a momentary or sustained short to its output.

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. Controls shall be oriented toward the face 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 175 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-IC1.