ISDN:
1. 4.1.2:
   E:Standard
   I:Terminology
   Q:Signal
2. BRI:
   2B: 64K each     (HDLC or PPP)
   1D: 16K control  (LAPD)
   total 144K
3. PRI:
   23B+1D+1F=1.544MB=T1 (24*64+8)
   30B+1D+1F=2.048MB=E1 (32*64)
4. 4.1.5 figures:
    R: TE2-TA
    S: TE1-NT2
    T: NT2-NT1
    U: NT1-CO  (2-wire)
    NT1: 4-wire / 2-wire
5. SPID, Q.931