I had fitted a complete new thermostat to my house where the old SCR receiver had developed a relay fault. Note this older type RF1 device has a pairing sequence with the SCR receiver where the battery trays must be closed in the correct order to correctly pair up - the sequence is right side tray closed first then followed by the left side tray - then the red light on the SCR should flash for 7x seconds to show the devices have paired.
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