Fisher TFM1000 pulse count detector-How does it work?

[djsb]

I'm trying to understand how the switch,pulse counter and averaging filter stage of the Fisher TFM1000 tuner works. I have read a copy of an article by A H Seidman from Electronics World Jan 1967 (link below). Attached is an LTspice file I have created in an effort to try to understand how the circuit works.
The first 3 limiter stages are straightforward. It is the switch, delay line, pulse counter and averaging filter  that I don't understand (centre around Q5,Q6 and L3 in the LTSpice schematic and Q905/906 and L902 in the original schematic). I have cross-referenced the article above with the service manual and L3 is just marked 500 (it does not indicate nH,uH, or mH). However, the photo of the unit shows a coil mounted on a ferrite rod. This could be the delay line. Could someone help me to figure this out? I'm just curious as to how this novel detector works and in particular how would a 25nS delay line be implemented as well. Thanks.

PS The text file attached is the LTSpice file. Please change the text file extension to .asc. The pdf file is a page from the service manual with the limiter/detector schematic. The article mentioned above is too large to upload. Here is a link to it
https://www.americanradiohistory.com/Archive-Electronics-World/60s/1967/Electronics-World-1967-01.pdf

[vk6zgo]

For a basic idea on how pulse counting FM detectors work, watch this:-