5T1A

The Tektronix 5T1A is a timing plug-in for the 661 sampling oscilloscope. The job of the 5T1A is to produce three signals: the sampling pulse, the horizontal sweep, and the blanking signal. The input to the 5T1A is a trigger signal. The trigger can arrive from any of four sources:

• internally from the trigger pick-off in a 4S1 plug-in
• externally via a GR-874 connector on the front panel of the 5T1A
• from the calibration oscillator in the 661, via the muliti-pin plug-in connector
• free-running

Each of these modes is suited to some measurement scenarios. In the case of internal triggering, the signal goes from the trigger pick-off in the 4S1 to a coaxial interconnect that passes through the 661, connecting the sampling unit to the timing unit.

Triggering in the 5T1A is accomplished using five 1N3129 20mA tunnel diodes.

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