Shopping trolley lock

I always wondered how these gatekeeper shopping trolley locks work.

After watching Dave Jones EEVblog #1287 i decided to post some photo's of the trolley lock system of a shop in The Netherlands, Almere.
The lock mechanism in Dave's video is inside one wheel. The system in this shop uses a red block mounted near a wheel.

The range for the trolley is indicated by a red line on the street.
It is amazing to see how far a way is the limit for a trolley this relative small shop.
According to Dave's video there should be a wire with an active signal at this red line.

Some years ago i had a trolley with a locked wheel and a shop employee unlocked it. Recently i noticed this device and also include
a photo of it.

It contains a link to interesting the website https://rocateq.com/ of the company Rocateq who makes  this device.
I also did some searches on internet and found a user manual
https://fccid.io/2AGTS-MRU/User-Manual/User-Manual-2850312 a download page of the company
http://www.rocatequsa.com/rocatequsa/Rocateq_USA__Useful_Downloads/Rocateq_USA__Useful_Downloads.html
with several interesting documents.
and YouTube is this video of the company
https://www.youtube.com/watch?v=ZRIqaB1ooF8

In the documentation two frequencies are mentioned
Frequency for locking & unlocking is 8.13KHz.
Frequency for mute is 318.06MHz