A typical Sigma module is shown alongside in the photograph.
This is a rigid mechanical assembly which supports the three major types of
components: 1) panel controls. 2) audio connectors. 3) electronic components.
Modules are secured in the frame at each end and may be removed for service
attention. On most Sigma modules any internal trim needing routine attention is accessible
from the front panel.
The circuit board assembly uses laminated epoxy glass fibre material of high strength.
The module panel is aluminium alloy, paint finished and screen printed. The panel is grounded
for screening purposes as are all potentiometer cases.