Consider the following statements regarding the human circulatory system and the functioning of the heart:

1. 1. Double circulation is found in the human heart, under which deoxygenated blood goes to the lungs for oxygenation through the aorta and oxygenated blood is pumped to various parts of the body through the vena cava.
2. 2. The 'Pacemaker', also called the Sinoatrial Node (SA Node), is located on the wall of the right atrium, which self-excites to generate electrical impulses and controls the rhythm of the heartbeat.
3. 3. The correct direction of blood flow in the human heart is 'Vena Cava $\rightarrow$ Right Atrium $\rightarrow$ Tricuspid Valve $\rightarrow$ Right Ventricle $\rightarrow$ Pulmonary Artery'.
4. 4. A sphygmomanometer is used to measure blood pressure, in which the systolic pressure of a normal healthy human is about 120 mm Hg and the diastolic pressure is about 80 mm Hg.

Which of the above statement(s) is/are completely true?