McDewey

(+5)+(™3 dBm0) = 8 dBm If the ™3−dBm0 signal is properly measured at the +5 TLP, the meter reads 8 dBm. In a similar manner, if a ™3−dBm0 signal is measured at the › TLP, the meter reads ™6 dBm: (TLP) + (Power at the 0 TLP) = (Power at the › TLP) (›)+(™3 dBm0) = ™6 dBm In order to determine the expected power at any given TLP, it is sufficient to know the power present at some other TLP in the circuit. And, just as the mountain does not have to be near the sea in order to determine its height, the 0 TLP does not have to actually exist on the circuit. This figure illustrates a circuit between two demarcs. A š9−dBm test−tone signal is applied at the ™6 TLP. What should you expect to measure at the +7 TLP? Even though the 0 TLP does not exist on the circuit, you can describe the power you see at the 0 TLP if it did exist: TLP)+(Power at 0 TLP) = (Power at the ™6 TLP) (™6)+(Power at 0 TLP) = š9 dBm (Power at 0 TLP) = ™3 dBm
Using the relationship again, you can determine the power at the + 7 TLP: (TLP)+ (Power at 0 TLP) = (Power at + 7 TLP) (+7)+(™3 dBm0) = ž dBm Use of the 0 TLP reference permits transmission objectives and measured results to be stated independently of any specific TLP, and without the specification of what the test−tone levels are to be or where the test tone is to be applied. This figure shows a test tone transmission from demarc A to demarc B.