It takes the form of a flexible silver collar and bracelet, usually joined by a long silvery leash, although lately revealed that that convention is not strictly necessary to its functioning.
"Setalle took the a'dam from Mat and fumbled at the flat segmented bracelet on one end of the round silver leash. The whole thing was made in segments, fitted together so cunningly you could not see how it had been done."
The first a'dam was made by Deain Sedai, a Seanchan woman who wanted to assist Luthair Paendrag Mondwin in his consolidation of the continent by giving him an instrument to control female channellers who opposed him. She was later collared herself by an a'dam, and it is said that her screams "shook the Towers of Midnight". While the exact timing of this event is unclear, it must have occurred in Luthair's lifetime, so sometime in the later days of the Free Years calendar.
The a'dam creates a link between the two female channeller; the wearer of the collar is completely controlled by the wearer of the bracelet. Latter is not even required to be able to channel on her own, only to have the ability to learn how to channel is enough for controlling the wearer of the collar.
An a'dam also works as a buffer so the damane would not be able to burn herself out. This was probably incorporated into the original device to prevent any possibility that a captive deliberately burn herself out and stop herself being used. In this way the Sul'dam are also able to Force the damane to reach quickly their full potential avoiding any damage to them.
Affect on society and life
Wearing the a'dam marks and defines the social status of female channellers in the Seanchan Empire; the leashed woman is called a damane (Leashed one), and the women who holds the bracelet a sul'dam (Leash holder).
At the time of the invention it was known that both women can channel, but later this knowledge was erased and become unknown. Seanchan people believe that only those women who born with the spark can channel. The fact that the a'dam 's nature as a ter'angreal required a woman who is capable of channelling was completely lost. Ironically, while damane are viewed by most as dangerous, subhuman property to be controlled, sul'dam are valued members of society due to their skill in working with the women who actually wield the One Power.
The recent rediscovery of this fact by certain members of Seanchan society (including some sul'dam) has the potential to rock their society to the core. However, as of by the time of the beginning of the Fourth Age, this information has not been widely disseminated.
Differences between willingly formed Link and the a'dam's created Link
The a'dam creates a circle of two female channellers led by the wearer of the bracelet. The lead cannot be passed over to the wearer of the collar, the woman who wears the bracelet is always leading the circle. The leader has complete control over the other woman's channelling ability, although the flow of saidar is woven by the damane. The sul'dam only command her to weave it. A sul'dam is able to feel her damane's emotions, physical reactions and being able to influence or change them through the a'dam, or would be able to combine her own abilities with those of the other woman to channel a single, combined set of flows herself. Due to the fact that sul'dam's channelling ability is forgotten in Seanchan, a'dam is used merely to control a damane and make her channel to command.
Gender mixed use
While a normally formed circle of one man and one woman is possible, wearing the bracelet of an a'dam causes intense pain to a male channeller and would usually kill him. No experimentation was done regarding a woman wearing the bracelet and a man wearing the necklace, but it might well have done the same thing. Touching a the a'dam worn by a woman would cause pain both to the woman and the man so that a male channeller cannot open the collar and free a damane by physically touching it. When a male channeller attempts to free a damane on leash all three experiences immense pain.
"He [Rand] put a hand to the collar of the nearest, and felt a jolt that nearly numbed his arm; for an instant the Void shifted, and saidin raged through him like the snowstorm a thousandfold. The damane's short yellow hair flailed as she convulsed at his touch, screaming, and the sul'dam connected to her gasped, face going white. Both would have fallen if not held by bonds of Air."
Meanwhile anybody who cannot channel can open both the bracelet and the collar, or remove the collar from a damane when she is not linked with a sul'dam.
"The catches were a simple matter for him [Mat] the bracelet easiest. That was just a matter of squeezing the right spots, top and bottom, not quite opposite the leash. It could be done with one hand, and the bracelet popped open on one with a metallic click. The collar was a little trickier, and required both hands. Putting his fingers on the proper spots on either side of where the leash attached, he pressed, then twisted and pulled while holding the pressure. Nothing happened, that he could see, until he twisted the two sides the other way. Then they came apart right beside the leash, with a sharper click than the bracelet. Simple. Of course, figuring it out had taken him nearly an hour, back in the Palace, even with what Juilin had seen to help."
A woman who only had the potential to be able to learn how to channel can't be brought into a normally created circle. Meanwhile an a'dam works immediately for them. That's why it is used to recruit sul'dam and discover damane. (Also it creates a possible contradiction.)
In a normally created link there is no feedback regarding the feelings, emotions of the participants in the link.
Burned out channellers
An a'dam has no effect on a person who is burned out and if she wears the bracelet it has the same effect on a damane as if a normal person would wear it. 
A'dam can be opened at a distance with the One Power, as discovered by Nynaeve at Falme.
The a'dam includes a number of useful characteristics for maintaining the captivity of the damane:
- It incapacitates the damane if she makes any attempt to open the clasp on the collar, or move an empty bracelet from where it has been placed by a sul'dam.
- It allows the addition of emotional sensations to the damane's worldview; she can thus be punished immediately and unavoidably for any transgressions, a fact used liberally in most training.
- Any pain inflicted on a sul'dam is also felt by the damane twice as severely, effectively preventing a damane from attacking her sul'dam.
- A damane cannot pick up a weapon. If a damane thinks of using an object as a weapon, she will not be able to pick it up until she completely expunges the thought from her mind.
- When the bracelet is not worn by a sul'dam, moving it will incapacitate the damane with pain and nausea. This prevents her from escaping even when unattended.
- A sul'dam can make a damane embrace or release the True Source at will.
- Damane are unable to form circles as other channelers can, because they are already linked with their sul'dam. This fact constitutes an extraordinary weakness with regard to using damane against other channelers.
Elayne Trakand created a unique a'dam in order to hold Moghedien captive. This example had a few special features allowing it to be kept secret. Most importantly, the bracelet and collar were in separate pieces instead of joined by a leash. Also, it apparently did not restrict Moghedien's movements when unlinked, because she suffered no ill effect when Elayne left the bracelet unattended in her room.
- Main article: Domination Band
A similar ter'angreal exists to allow control of male channelers. It consists of a collar and two bracelets, in separate pieces, all made of black cuendillar. Though it has been referred to as an "a'dam for men," it should be noted that it dates from the Breaking Of The World, centuries before the a'dam was invented. This version of the device allows for far more control over the subject, but it requires two women to maintain that control as opposed to one. If only a single woman attempts to use it, a high degree of possibility exists that the device will, given time, give the subject complete control over whomever is wearing the bracelet.
Originally only one such set was known. This fell into the possession of the Seanchan, who made at least six copies.