This read-write control starts or stops traffic flow on the inbound and/or outbound ATMizer (the segmentation-and-reassembly, SAR, hardware) for this circuit without notifying the PPC (the circuit's higher-level control processor), essentially a low-level diagnostic knob for isolating SAR-layer behavior independent of the rest of the call/circuit control stack. This is a diagnostic tool rather than a normal operational setting, letting a technician selectively block or allow inbound/outbound cell flow at the SAR level to isolate where in the pipeline a problem lies, without the PPC's normal state-tracking interfering with the test. An engineer debugging whether a reported cell-loss issue originates in the SAR hardware or further up the stack might set cktDiagSARMon to flowOffOutbound(4) to silence outbound flow and observe whether the PPC's own counters still show activity.