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Simple Cat.5 Network Tester(SN74LS153N)

2015-01-09 00:16  
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This article describes the Simple Cat.5 Network Tester (SN74LS153N). The principle is very simple, very practical. The circuit components can help you understand better grasp this principle. For example, in this circuit, you can go to find and buy these components: SN74LS153N.

This circuit came from a need for a “quick and dirty” network tester that could be operated by one person. All the commercial units I tried required a person at the other end to check the remoteLEDs, as the transmitters could not be made to cycle through the test continuously to allow one person to check both ends. It must be noted that this unit will only check for pair continuity, pair shorts, crossed wires, and shorts to other pairs. It will not test bandwidth, etc. Operation is fairly basic.

Circuit diagram:

Figure:1 Simple Cat.5 Network Tester

Figure 1 Simple Cat.5 Network Tester

Half of the 4011 quad 2-inputNANDgate is an RS flip-flop (IC1a, IC1b) which controls the other half, IC1c & IC1d, operating as a clock oscillator. You can either start and stop the oscillator running by pressing the Start and Stop switches or by virtue of diode D1 connected to pins 12 & 13, use the Stop switch to allow manual clocking of the 4017 counter. The 4017 drives one of eightLEDs and the lines to the RJ45 socket. An output “High” on the 4017 decides which line is under test, and if the circuit is complete, the testLED’s current is “sunk” by the 4017 and theLEDwill light.

If the corresponding testLEDon the remote fails to light, then there is a short of that pair in the cable under test. If more than oneLEDlights, it indicates a short with another pair. A dark testLEDon the transmitter indicates that pair is open circuit. “Start” starts the circuit cycling at a rate determined by the 470nF capacitor and 220kO resistor and “Stop/Step” stops cycling, steps through the lines, and when stepped so that no channelLEDs are alight, effectively switches the unit off with a standby drain current of less than a microamp.



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