国际10-20系统
10-20系统包含19个记录点击和2个参考电极A1, A2。
Derivation
derivation代表为了表达一个通道，用于组织电极的方式。一共有3种derivation：
Monopolar derivation
又叫做Referential Derivation。
这种derivation使用耳朵A1和A2作为参考电极。也分成几种参考方式。
- normal monopolar derivation。左耳用于左半球参考，右耳用作右半球参考。
- A1+A2。 shorting both ears(in the electrode junction box)
- A1→A2 or A1←A2。只使用一只耳朵。
- A1<->A2。左耳作为右半球参考，右耳作为左半球参考。
- Vx (vertex reference derivation)。也就是以头顶处Cz为参考点。
- AV（Average reference derivation)除去几个特殊输入例如（X），BN+， BN-，其余的全部头皮电极使用resistors(电阻)形成一个平均点。额外的特殊输入根据electrode junction box具体情况不同，实际操作中应该把心电，肌电等去除*
参考3.16
BN Derivation
全名Balanced Noncephalic Reference，平衡式非头部参考电极。
Bipolar Derivation
A1 → A2: Switches all A1 to A2. A1 ← A2: Switches all A2 to A1. A1 ↔ A2: Switches A1 and A2. A1 + A2: Short-circuits A1 and A2 to each other in the electrode junction box. Vx: Switches all A1 and A2 to CZ. AV: Switches all A1 and A2 to the reference for AV derivation. BN: Switches all A1 and A2 to the reference for BN derivation. (Available when the JE-208A or 210A is used.) SD : Switches all A1 and A2 to the reference for Laplacian derivation. Aav: Switches all A1 and A2 to the averaged reference of A1 and A2. Org: Switches all A1 and A2 to the averaged voltage of C3 and C4 for the original reference derivation (system reference). OFF: Cancels the selection of reference electrode and returns to the programmed setting.