What I was referring to is the C.O. switch or the Class 5 switch. Maybe different companies use different terminology. Tandem switches that I dealt with were further up the chain. They had trunk fields terminating from and to the Class 5 offices. They routed the calls between Class 5’s and to other Tandems. What I was used to was in the 5E world was you had the Host or stand-alone switch. You had RSMs (Remote Switch Modules) or ORMs (Optical Remote Modules) that were connected to the host. The RSMs connected via T1 umbilicals. If memory serves me correctly the ORMs connected by a minimum of 4 T3s. There may be newer technology available now. In the DMS there were similar configurations. The remotes used to be referred to as REMs.

The DMS or 5E Host handles the bulk of the billing and trunking. The generic program resides in the central processor of the Host or stand-alone switch. The various types of remote switches function in much the same manner as an SM or PE Bay in the Host C.O. They can continue to process calls if the path to the Host is cut. The call processing is usually limited to calls within the module. There could be some calls outside the module if it is equipped with any trunking equipment. Usually a 911 emergency function is available.

Gary