delta modulation
1 bit DPCM
2 levels for quantizing
because only 1 bit, framing not necessary

single steps only, very simple, 2 types of errors: slope overload (m(t) changes too quickly), granular noise/quan noise, occurs when sig isn't changing much
step size is a tradeoff
big steps react better to slope changes, small steps decrease granular noise

on-off NRZ
10011101
-__---_-

polar NRZ
-  --- -
 --   - 

polar has slightly better error performance
on-off RZ
1 0 0 1 1 1 0 1
-_____-_-_-___-_

polar RZ
-     - - -   -
 ----- - - --- -

use RZ for clock sync issues

bipolar NRZ aka, AMI
10011101
-__ - _-
   - -

manchester down transition for 1, up trans for 0
1 0 0 1 1 1 0 1
-  - -- - -  --
 -- -  - - --

power density spectrum of line codes
sig is sequence of pulses, amp of pulses convey info, pulse is arbitrary but time-limited to [0,T]


energy spectral density