New for 2025 is a signal sensing power switch. This is detects a low level signal ( approx. 200uV @200Hz) and switches on a power relay. This relay is chosen to handle up to 30A of inrush current. The load will usually be an audio power amplifier. The sensor will latch with less than 1 second of input signal and will stay latched for up to 10 minutes once the audio input signal has been removed. Clearly the sensing signal will need to be free from residual hum and noise.

The relay has single pole and for reasons of safety need to be used with class 1 equipment, i.e., those with and earthed metal chassis. The PCB has two a stereo input but using just one is quite sufficient unless one channel of a stereo system is switched off. The control side of the PCB has its own switch mode PSU which is very efficient and will standby at less than 0.5W. The PSU has the recommended input filter capacitor to comply with EMC regulations. A 1A slow blow PCB fuse protects against PSU failure.
The audio sensing circuitry is floating from mains ground to avoid ground loops. The PCB has the required clearances (insulation gap) for safe floating operation. The installer needs to be aware of good practice for safety at hazardous voltages. PCB support pillars should be nylon. If a metal box is used, it should be bonded to the mains ground and the input connectors should be isolated from the chassis. A plastic housing box is ideal if class 2 construction is followed. The PCB ground plane helps to avoid capacitively induced signals causing a false “on” condition. However, this means the plastic box will need to avoid high AC fields, and not run close to mains cables.
Connectors are screw terminal type and ferrules are not essential as the internal blades protect the wires from chafing when tightened. Care is needed to avoid stray strands. Tinning the just the end 1mm tip of the wire (not all of it) can stop stranding problems. The PCB carried two LEDs. The green shows incoming power. The red will light also when the relay is connecting mains power to the outlet connector.
The recommend build will have a fused IEC inlet C14 and one or more IEC type outlets C13.
PCB dimensions 100 x 75 mm. PCBs supplied built and tested. Guarantee 1 year.