The Tektronix 7D14 is a 525 MHz frequency counter plug-in for 7000 series mainframes.
It uses the mainframe's readout system to display an eight-digit count on the CRT. Modes include frequency, frequency ratio and events count using manual or external gate.
When installed in a horizontal compartment, it can count the trigger pickoff from a vertical amplifier unit. This allows simultaneous viewing and counting of a signal in four-bay mainframes.
In a vertical compartment, the trigger signal (i.e. the "shaped" input) can be displayed as the module's Y output.
|Frequency||525 MHz (5 MHz bandwidth limiting switch available)|
|Sensitivity||100 mV to 10 V|
|Input Impedance||50 Ω or 1 MΩ // 20 pF on external input, 1.5 Div internal when set to "Trig Source"|
|Gate time||1 ms to 10 s|
|Display time||0.1 s to 5 s or infinite|
An input section using relays selects the counter signal from the internal trigger path or external input, and activates 50 Ω termination and/or attenuators.
A differential FET buffer + bipolar amplifier stage drives a counter gate that uses a 10 mA tunnel diode as the switching element.
The first decade is implemented as a divide-by-2 ECL flip-flop (156-0377-00) followed by a 5-stage ring counter made with discrete transistor pairs (note circular layout) and some logic to BCD-encode the count result.
The following seven counter stages are conventional TTL decade ripple counters (N8292A).
The counter outputs are multiplexed onto a common 4-bit bus using open-collector NAND gates under control of the mainframe's readout system. The multiplexed digit value feeds a D/A converter (Tek 155-0038-01) that in turn drives the analog row and column returns to the readout system. A separate blanking logic eliminates leading zeroes and displays a ">" sign in the leftmost column if the counter overflows.