Paging Sound Detector

The RDL TX-PSD1 Paging Sound Detector monitors an amplified speaker-level source and activates an open-collector control output when the selected signal threshold is reached. Its transformer-coupled input supports constant-voltage speaker lines, while front-panel sensitivity and release-delay adjustments provide direct control over detection and output timing.

Ideal Use Cases

The TX-PSD1 is designed for systems in which paging or another amplified audio signal must initiate a switching function. It can monitor an existing 25 V, 70 V, or 100 V speaker line and trigger its control output when audio is detected. The 25 V input setting also accommodates 8-ohm sources rated up to 75 watts, extending its use beyond constant-voltage distribution systems.

• Detecting activity on paging speaker lines
• Initiating switching functions from amplified audio
• Monitoring 25 V, 70 V, or 100 V distributed audio systems
• Detecting an 8-ohm amplified source up to 75 watts through the 25 V setting

Why Choose This Model

The switch-selectable input makes one module suitable for three common constant-voltage speaker-line formats. Transformer coupling isolates the audio input, and the adjustable trigger threshold allows the detector to be matched to the level present on the selected speaker line. A red threshold LED assists with sensitivity adjustment, providing immediate visual feedback while the module is configured.

Once triggered, the TX-PSD1 activates an open-collector output rated at 25 mA through the SLAVE terminal. Its release delay is adjustable from 3 to 25 seconds, allowing the control output to remain active for a selected period after detection. A green LED shows when the module is triggered, while a blue LED confirms power status.

Installation and Integration

Installation begins by connecting the transformer-coupled audio input to the amplified speaker line and selecting the appropriate 25 V, 70 V, or 100 V input setting. For an 8-ohm source up to 75 watts, the 25 V position is used. The module requires ground-referenced 24 Vdc power at 20 mA. Recommended power supplies are the PS-24AS for the USA and the PS-24AX for international use; the power supply is not included.

The front-panel sensitivity trimmer is used to establish the desired detection point. During setup, the red threshold indicator helps show when the incoming audio reaches that setting. A separate front-panel trimmer sets the release delay between 3 and 25 seconds. The open-collector output is available at the SLAVE terminal for connection to the applicable control function.

The module measures 3.17 inches wide, 1.76 inches high, and 2.06 inches deep. The listed metric dimensions are 8.05 cm wide, 4.47 cm high, and 5.23 cm deep. Functional block, front-panel, and rear-panel CAD files are identified as available in American DXF format.

Performance Highlights

The TX-PSD1 detects audio across a specified bandwidth of 120 Hz to 7.5 kHz at the -3 dB points. Its adjustable trigger-threshold specification is listed as 40 dB to -15 dB below the selected 25 V, 70 V, or 100 V input level. Both threshold and release-delay controls use single-turn adjustment.

Three color-coded indicators support operation and setup: a blue LED for power, a red LED for the signal threshold, and a green LED for the triggered state. Together, these indicators show whether the module is powered, whether the adjusted threshold is being reached, and whether the control output is active.

What Makes It Different

This model combines speaker-level detection, transformer isolation, adjustable sensitivity, adjustable output timing, and an open-collector control output in one module. It accepts amplified constant-voltage signals directly rather than limiting detection to one speaker-line voltage. Its 25 V setting adds compatibility with 8-ohm amplified inputs up to 75 watts.

The independent threshold and triggered indicators distinguish the setup state from the active control state. This allows the sensitivity to be adjusted using the threshold LED while the separate green indicator confirms actual triggering. The 3-to-25-second delay provides a defined, adjustable release period for the output.

Final Assessment

The RDL TX-PSD1 is a focused control module for turning paging or other amplified audio activity into an open-collector switching signal. Its selectable 25 V, 70 V, and 100 V input, transformer-coupled connection, adjustable threshold, visual status indicators, and configurable release delay provide the essential controls needed to integrate speaker-line detection into an audio control system.