### Instruction:

Extract the cause and effect entities from the following sentence:
During this recovery period, the system shall not permit the use of unverified functional numbers

### Assistant:

KEYWORD: During
VARIABLE: the system
NEGATION: shall not
CONDITION: permit the use of unverified functional numbers
CAUSE_1: this recovery period
EFFECT_1: the system shall not permit the use of unverified functional numbers

