QRSS (or QRS, QRTS, QRW) is a basic test pattern used to test DS1 circuits and equipment for continuity and performance. QRSS is the most commonly used test pattern for T-1 maintenance and installation. This pattern will stress timing recovery, ALBO and equalizer circuits, but it also simulates customer traffic on the circuit. The QRSS pattern can be used framed or unframed and will force a B8ZS code in circuits optioned as B8ZS.

The QRSS pattern is a psuedo-random 1,048,575 bit sequence (2^20-1) generated by a 20 stage shift register with feedback taken from the 17th and 20th stages. The output signal is taken from the 20th stage, and the output bit is forced to be a one whenever the next 14 bits are zero. The QRSS pattern has an average ones density of 50% and contains high density sequences, low density sequences, and sequences that change from high density to low density and vice versa. On circuits optioned for B8ZS zero substitutions will occur.

Stands for Quasi-Random Signal Source. Also called Quasi by techs when talking to each other.