Used Boss WL-20, like new. This sale includes the receiver and transmitter. I've used this unit in many live situations (with lots of people and neon and smart phones and electronics and band mates' wireless systems) and never had any problems with noise or lost signal. It uses the 2.4 GHz frequency range and Boss claims the WL-20 has a 50ft. line-of-sight range. I never moved more than 10 feet away from the receiver, so I cannot confirm the range limits. At most, I've used this unit for 4 hours continuously with no concerns over battery life. I've only used this WL-20 for about a year, so there's still plenty of recharging life in these batteries.
Pairing the receiver to the transmitter is easy; just plug the transmitter into a jack on the receiver. Pairing only takes a few seconds. The receiver has two lights and the transmitter has only one light. To turn off the units, just unplug them. Both transmitter and receiver has an "auto mute" switching system where they automatically stop sending/receiving a signal when unplugged. That means, if you unplug from your guitar you won't hear any noise from the transmitter when you touch the jack while switching to another guitar. No need to re-pair the units when plugging or unplugging them. I would just pair the receiver and transmitter at the start of a show and be good for the whole night even after switching guitars.
I'm selling this unit because I recently bought a Strandberg guitar and the placement of the cable jack is such that the WL-20 is uncomfortable. The WL-20 has no articulation, so while it works fine with Strats, Teles, Les Pauls, SGs, Jaguars, Jazzmasters, etc., it's not ideal for the Strandberg where the cable jack is behind the guitar.
More information here:
https://www.sweetwater.com/store/detail/WL20--boss-wl-20-digital-wireless-guitar-system-with-cable-tone-simulation
The WL-20 is just like the WL-20L, but the WL-20 adds "cable tone," which mimics the way a length of cable (maybe 10') might impact your sound. This has the effect of slightly "warming" your tone so it sounds less sterile. Compared to 10 feet of Mogami Gold cable, the WL-20 is very slightly brighter. Otherwise, there is the same amount of articulation and tone transmitted to the amp. Unfortunately, the WL-20 does not eliminate single-coil/60-cycle hum; that would be nice.