This enables or disables whether this DS1 port will honor inband loopback commands sent to it by far-end equipment, without affecting this port's own ability to send loopback commands outbound to the far end. Disabling this on a specific port is a protective measure against an untrusted or misbehaving far-end device remotely forcing this port into loopback and disrupting live traffic, while still letting an admin here initiate loops toward the far end whenever needed for testing. A carrier demarcation port exposed to customer-owned CPE might have pportds1FELoopbackControl disabled so the customer's equipment cannot inadvertently or maliciously loop this port, while the carrier's own test equipment on this switch can still command loops toward the customer.