The Strand Electric Junior Interlock JI/24 represents an important period in the development of stage lighting control, when manually operated resistance dimmers were being combined with increasingly sophisticated mechanical control systems.

The JI/24 provided 24 lighting control channels sharing 12 Sunset dimmers. Each channel could be selected full on, off or on dimmer, allowing the available dimmers to be shared between a greater number of lighting circuits.

The twelve dimmers were mechanically interlocked to two master wheels. Individual lighting levels could therefore be set using the dimmer handles, while groups of dimmers could be operated together from the master wheels to produce coordinated lighting fades.

Strand described this as a ‘cordless’ circuit, allowing all of the selected channels to be faded in or out simultaneously.

The surviving engraved labels on this example, including SPOT, BAT, F.O.H., DIPS and PATCHING PANEL, provide a fascinating reminder of its original working installation and the way in which the board was configured for use.

The Junior Interlock JI/24 appears in Strand’s 1963/64 Lighting for Entertainment catalogue and remained in the company’s range into the mid-1960s. By 1966, a new JI/24 was listed at £297.

The Junior Interlock belongs to a period of transition in stage lighting control, when sophisticated mechanical dimmerboards continued to be developed and used alongside the emerging generation of remote and electronic control systems.

Today, this example forms part of the Historic Stage Lighting Collective Collection, preserving another chapter in the development of British stage lighting and control.