In a J-K flip-flop, if both J and K are tied to same input, then the derived Flip-flop becomes T Flip-Flop (shown below ).
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This has only one input which is called T-input.
| Input Tn | Output Qn+1 |
| 0 | Qn |
| 1 | NOT (Qn) |
When T is 1 this flip-flop becomes a toggle flip-flop, and the output Q keeps toggling on every clock edge(-ve). T Flip-flops are used in synchronous counter circuits.