*------------- send 0
            |
  *---analog switch---*--- line
  |                   |
 | | 110 Ohms less   | |
 | | Ron of analog   | | 70k
 | | switch          | |
 | |                 | |
  |                   |
  |                   *---input
  |                   |
  |                  | |
  |                  | | 50k
  |                  | |
  |                  | |
  |                   |
  *-------------------*---Gnd