This work describes a new model of phase locked loop (PLL), which is based on the measurement and processing of the common time interval of the input and output periods. In the class of the time recursive PLL, this PLL is the simplest one for the realization. PLL is described by three output variables. All mathematical analyses are performed using the Z transform approach. The region of parameters for the stable system is presented. Depending on the choice of the system parameters, PLL can be used as the powerful and precise phase shifter in the noise rejection applications, in the applications with short or adapted transient time and in others. Computer simulation of PLL is made to enable better insight into the PLL properties. The realization of PLL is described.

Keywords: Phase locked loop (PLL), Frequency locked loops, Phase shifter, Digital circuits