Question:  When gap extension is programmed, do cities generally use the detectors to have this signal timing setting, or do cities program the controllers to have this setting?

Answer:  I’m used to thinking in terms of Gap Reduction.  Gap Reduction is done entirely in the controller unit inputs.

Extension is a term that is usually applied to a detector input.  Extension can be done either in the Detector Sensor (the part that sits in the rack/shelf in the controller cabinet), if it is the programmable type, or in the controller unit inputs.  It is very easy to program most 2070 or ATC controller units for detector extension.  170s are a little harder because the programming is done by detector input channel number, not by phase.  Older NEMA units may not have this controller input, so it has to be done with the detector sensor.