The circuit comprises transmitter and receiver

The circuit comprises transmitter and receiver, the cable under test linking the two. The transmitter is nothing more than a “LED chaser” the 4011 IC is wired as astable and clocks a 4017 decade counter divider. The 4017 is arranged so that on the 9th pulse,the count is reset. Each LED will light sequentially from LED 1 to LED 8 then back to LED 1 etc. As the 4017 has limited driving capabilities, then each output is buffered by a 4050. This provides sufficient current boost for long cables and the transmitter and receiver LED’s. The receiver is simply 8 LED’s with a common wire…read on.

The 4011 is a member of the 4000 Series CMOS range, and contains four independent NAND gates, each with two inputs. The pinout diagram, given on the right, is the standard two-input CMOS logic gate IC layout:
Pin 7 is the negative supply
Pin 14 is the positive supply
Pins 1&2, 5&6, 8&9, 12&13 are gate inputs
Pins 3, 4, 10, 11 are gate outputs

The truth table for one of the four gates is shown to the right. For more infomation about the NAND gate in general, see this module.

This chip is widely available, and usually comes in a DIL-14 or SOIC-14 package.

This chip is different in pinout to the TTL 7400, but can fulfill its function if the wiring is modified.