How enable scramble on Cisco SONET interface

Scrambling for POS interfaces is set on the interface itself. It is not a controller option..
 

Cisco Router# sho int pos5/1
POS5/1 is up, line protocol is up
  Hardware is PM5351 S/UNI-TETRA-155 Framer
  MTU 4470 bytes, BW 155000 Kbit, DLY 100 usec,
     reliability 255/255, txload 56/255, rxload 49/255
  Encapsulation FRAME-RELAY, crc 16, loopback not set
  Keepalive set (10 sec)
  Scramble enabled

Command Syntax
 

To Enable Scrambling:
 

Cisco Router(config)#int pos5/1
Cisco Router(config-if)#pos scramble-atm
 

To Disable Scrambling:
 

Cisco Router(config)#int pos5/1
Cisco Router(config-if)#no pos scramble-atm