ST-SSR1 Line-Level Audio Switch
The line-level audio switch shall be an RDL ST-SSR1. The unit shall provide two balanced inputs, one balanced output and a provision for remote source selection.

Line inputs shall be electronic balanced bridging with an input impedance no less than 20 kOhms and an input level of +4 dBu and shall be fully compatible with either an unbalanced or balanced audio source. No gain shall be applied to the input signals.

One input shall be routed to the output in the absence of an external source selection connection. The foregoing input shall be switched off and the other input shall be routed to the output when an external connection to the unit ground is applied to a trigger terminal by either a contact closure or by an open-collector requiring current sinking of no more than 0.5 mA. Switching shall not allow one input to turn on prior to the other input turning off.  Turn on time shall not exceed 20 uS and turn off time shall not exceed 15 uS.  The unit shall be equipped with a terminal to extend the switching transition to a ramped “soft” switching with a minimum turn on time of 35 mS and a minimum turn off time of 5 mS.  Two LED indicators shall be provided, one corresponding to each input. Each LED shall illuminate when the associated input is active. 

The unit shall provide a line input audio frequency response of 15 Hz to 20 kHz (± 0.5 dB) with total harmonic distortion plus noise of <0.05% (20 Hz to 20 kHz) and a noise floor exceeding 80 dB below the normal rated output level. Each line input shall provide common mode rejection at 100 Hz of greater than 45 dB. The unit shall provide headroom of no less than 18 dB above the normal rated output levels.  Attenuation of the inactive input shall be greater than 80 dB from 10 Hz to 20 kHz.

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 and shall be capable of driving a 600 O load. The output circuit shall be configured to produce an unbalanced output of proper phase between the positive output leg and ground. The gain between any selected balanced input and the balanced output shall be unity nominal.

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.

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 40 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-SSR1.