Simple Cat.5 Network Tester

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 remote LEDs, 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:

Simple Cat5 Network Tester

Simple Cat.5 Network Tester

Half of the 4011 quad 2-input NAND gate 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 eight LEDs
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 test LED’s current is “sunk” by the 4017 and the LED will light.

If the corresponding test LED on the remote fails to light, then there is a short of that pair in the cable under test. If more than one LED lights, it indicates a short with another pair. A dark test LED
on 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 channel LEDs are alight, effectively switches the unit off with a standby drain current of less than a microamp.

Author: Craig Stephen – Copyright: Silicon Chip Electronics

Sorry, comments are closed!