The ST-SSR1 is a compact 2x1 line-level audio switcher designed for silent switching between two balanced inputs to a single balanced output. It provides zero-contact solid-state switching to avoid mechanical relay artifacts and audible clicks. The module supports unbalanced connections when required and preserves signal integrity across professional audio systems. Key features include two balanced line-level inputs, a balanced output, and user-selectable switching behavior that offers either fast or soft transitions. The SELECT input feeds the OUTPUT when the TRIG terminal is grounded; otherwise the OUTPUT is fed by the NORMAL input. LED indicators show the active input so system status is visible at a glance. Performance metrics include nominal +4 dBu operation, THD+N below 0.05%, and headroom greater than 18 dB above nominal levels. Frequency response is essentially flat from 15 Hz to 20 kHz under bridging loads and remains within ±0.5 dB across standard audio ranges. OFF attenuation exceeds 80 dB ensuring effectively muted inputs when deselected. The ST-SSR1 accepts control from simple grounded TRIG circuits requiring less than 0.5 mA, enabling control from open-collector logic, switches, or remote panels such as the RDL D-RC2ST and D-RT2. Terminals are provided for balanced inputs and output on a terminal block for secure connections in rack or enclosure installations. The unit is powered by a ground-referenced 24 Vdc supply at 40 mA. This switcher is suitable for applications that require silent source selection and reliable muting, such as broadcast studios, conference systems, and live production environments. It performs reliably where audio continuity and low-noise switching are required and integrates easily into existing signal chains. The compact package and low power draw simplify deployment in rack systems and distributed installations. Installation is straightforward with clear control logic and minimal wiring requirements. The ST-SSR1 operates in ambient temperatures from 0 C to 55 C and ships in a small cardboard package for simple storage. The design emphasizes dependable operation and predictable switching behavior in professional audio workflows. Specifications: | Inputs (2): | 20 kO balanced +4 dBu nominal | | Audio Output: | +4 dBu nominal 150 O balanced terminal block | | Switching Time: | Fast / Soft | | Time required for NORMAL input to turn cff: | 10 us / 5 ms | | Time required for NORMAL input to turn on: | 15 us / 70 ms | | Time required for SELECT input to turn off: | 15 us / 10 ms | | Time required for SELECT input to turn on: | 20 us / 35 ms | | Control Signal: | TRIG terminal must be externally pulled to ground | | Control Current: | 0.5 mA | | THD+N: | < 0.05% | | Frequency Response: | 15 Hz to 20 kHz (± 0.5 dB bridging load) | | Frequency Response: | 30 Hz to 20 kHz (± 0.5 dB 600 O load) | | Noise (below -4 dBu): | < -80 dB (85 dB typical) | | Headroom (above +4 dBu): | > 18 dB | | CMRR | > 45 dB (100 Hz either port) | | ON Gain: | Unity (600 O balanced input/output) | | OFF Attenuation: | > 80 dB (10 Hz to 20 kHz either input) | | Indicators (2): | LED showing active input (left LED=NORMAL; right LED=SELECT) | | Ambient Operating Environment: | 0 C to 55 C | | Power Requirement: | GROUND-REFERENCED 24 Vdc at 40 mA | | Package Type: | Cardboard Box | | Package Dimensions: | 2x2x4 in. | | Shipping Weight: | 0.198 lbs. | | WEEE weight: | 0.145 lbs. | | 
