11T84
The Tektronix 11T84 Time Coincidence Trigger is a prototype 11k plug-in that did not go into production.
The 11T84 was preceded by a prototype called the Universal Trigger Unit. Regarding this, Clark Foley recalls:
There were two fully authorized right-slot plug-ins for the 11300 series.
One project was called the Universal Trigger Unit (UTU). The UTU was a very ambitious project that relied on the Tek GaAs IC process. All of the signals from the left and center slots were buffered and delivered to the right slot as Auxiliary Triggers. You will see these signal pins in the Plug-in Interface schematic number 1.
After thirty years, I am sure to have forgotten some of this, but here is what I remember. The UTU was fully implemented (well, nearly) and only functional in the 11300 mainframes. This was important because the UTU did not have buttons or knobs. The UTU was similar to an FPGA but you could reprogram or edit the logic in real time and observe the output immediately. If you could describe an event as a combination of time and logical expressions at arbitrary voltage levels, you could detect it with the UTU. Implemented with GaAs and Tek's high-speed silicon processes, this thing was fast and power hungry. I have forgotten the exact speed of the logic, but I think it was on the order of 500 MHz.
The project met its end due to the GaAs process itself. We needed to be able to set multiple voltage levels for comparators that had to remain stable regardless of signal duty cycle and rep rate. Unfortunately, the GaAs process exhibited large variation in bias level as duty cycle and rep rate changed. When faced with a major re-design and compromise in speed, the cost-time versus value ratio wasn't high enough for such an esoteric instrument.
Later, and as more of an after thought, there came the 11T5H. It was created to give video triggering to the 11400-scopes. It functioned in the 11300-series scopes but was only necessary if HDTV was the application.
Also remember that the right-hand slot can drive the trigger path to the counter-timer hardware. It is possible to condition the signal with an 1000-series amplifier and direct it to the counter-timer. The trigger comparator output can be displayed on the scope as a Counter In or Gate signal. You can trigger the main and dly'd sweeps (forgive me, I meant Window) from the right slot.
