I've been "monitoring" public safety for over 45 years as my father was "career" LAPD. At 10 years old in 1965 I'd tune my GE "radio" to the VHF band and listen to LAPD dispatch and for his unit while the Watts Riots were going on.
My first "Scanner", around 1970 was a GE All band tunable radio that had 4, count them, 4 LED presets that I had programmed to Burbank Police and Fire VHF frequencies and could be "scanned" at lightning speed, about 4 seconds per channel.
Crystal scanners would follow. My first truely programable scanner was a Regency 16 channel base, VHF only of course.
Scores of scanners would follow that, base units and handhelds. I had always been partial to the Regency brand which was bought out by BearCat, but have had many Radio shack, Fannon and AOR scanners as well. I had been a member of the RCMA (Radio Communications Monitoring Association) for many years.
In the late 70s, early 80s, one scanner that really stood out was the BearCat 300 which was 100 channel, 800MHz scanner with built in squelch break taping capablility. I could press the tape button on the recorder and walk away. Only transmissions would tape. Mobile/Cellphones were in their infancy and only the rich and famous could afford them so it would be very interesting to listen to that area of the spectrum. Monitoring those frequencies was still legal and I had taped conversations of many celebrities using cell sites very close to me located near the Disney, NBC and Warner Bros studios, including Barbara Streisand, Richard Dryfus and Dudley Moore. What was contained in the conversations, the Inquirer and other tabloids would kill for. But of course disemanating information heard over the scanner to those who were not party to the original reception over the scanner is illegal.

VHF would lead to UHF. UHF to 800 MHz. 800 MHz to 1.2 GHz to even ALL BAND scanners. Trunking would arrive and now digital. 4 channels, 10 channels, 16 channels, 20 channels, 50 channels, 100 channels, 500 channels, 1000 channels and now Dynamic Allocated Memories that handle 1000s and 1000s of frequencies. Boy have things changed over the years.
Today, my scanners of choice are my BCD396XT handheld and BC796D base unit. EVERYTHING in Burbank, Glendale and many other cities and agencies, including LAPD, have now gone digital and digital scanners are a requirement. Unfortunately, digital scanners are very pricey and fewer and fewer people get into the scanner and monitoring hobby. Thankfully the cities and agencies I listen to didn't go digitally "encrypted" as Santa Monica and much of Orange County did.