Shock collars are collars that fit around a pony's neck and will deliver an electric shock on a certain stimulus. Most commonly a shock will be delivered via remote control by a trainer. In this case, the intensity and duration of the shock can be adjusted by the trainer.
When shock collars are used in ponyplay they are nearly always dog training collars used on humans. These dog training collars are designed to deliver eletric shocks based on any one of three criteria:
Straight from the box, I think the remote control version is the only shock collar with any real value. The stock bark collar is very difficult to activate when worn by a human - even when yelling.
The fence type collars can be effective when set up properly, but their use is fairly limited. The remote control collars, on the other hand, are quite versatile. Thus, I will focus on them here.
The first modification I made with my shock collar was to get rid of the ugly and insecure (i.e. not lockable) nylon. To do this, I purchased a plain leather dog collar and used a leather hole punch to add two holes in the center of the collar. Then I removed (you just have to unscrew to prongs) the shocking unit from the provided nylon collar and put it on the leather collar.
Although you could use a lockable bondage collar instead of a regular dog collar, I couldn't bring myself to punch holes in any of my nice bondage collars.
Luckily, it turns out a normal leather collar is easily lockable. Simply buckle the collar, feed the excess through the other side of the buckle and throw a padlock through one of the holes (see photo above and below right).
This might not be the most elegant solution, but it is effective: the collar is not coming off without a key.
Another thing I discovered is that the standard prongs are too long for use on humans (our necks usually do not have much fur). With the provided prongs, the collar has to be fastened incredibly tight to prevent the wearer from simply pulling the prongs out of contact with the skin. Moreover, at that level of tightness, the prongs will dig into the skin and leave marks (not ideal if you are wearing the collar around your neck - the marks may take hours to days to go away).
My suggestion would be to buy a shorter prong that is a little more blunt. This will allow for longer term wear, but still allow the collar to reliably deliver shocks. One thing to keep in mind though: the larger the area in contact with the skin, the less painful the shock. Thus, you may need to up the power to get the same sensation when you have a more blunt electrode.
The shocks from the collar feel like being pricked with many tiny needles. Increasing the power keeps the same subjective sensation, but increases the intensity of the pain (almost like being pricked with many burning needles). Shock collars can be surprisingly effective. For something that can cause so much pain, the shocks rarely leave any evidence: if the electrodes are blunt, I rarely see any marks after removing the collar - even after the most intense pain. It's a little scary - it's almost like a license for my trainer to be as sadistic as she likes.
You can also easily modify a shock collar to create an electrified bit gag, which is something I have recently tried. However, after having my trainer use it on me (an even on the lowest setting at that), I think I might like to uninvent this device.
I really like electrical play and have tinkered around with all three types of shock collars. I've even hooked them up to a modified butt plug resulting in dual stimulation of the neck and ass. That combination can really get a pony moving!
If you're willing to put some time and effort into it, you can create a combination collar that will deliver a shock to the neck (and an electrified butt plug, vaginal plug, urethral rod, or whatever else you might like) on any of the above the criteria. Indeed, you can even permit equine sounds (based on volume, frequency, etc.) while excluding human speech. Anyway, I'm digressing here, but I like electrical play and still really enjoy my basic shock collar.
Please keep safety in mind if you do decide to try one of these collars. They have been designed for use on dogs not humans. Aside from the positioning of the prongs, there is also a real risk of electrical burns. Be aware of all the risks inherent to electrical play and shock collars in particular.