Step 1: Understand the question:
External recruitment means getting candidates from outside the organisation.
We explain casual callers, employment exchange and advertisement as three such sources.
Step 2: Casual callers:
Job seekers sometimes apply on their own even though no vacancy has been announced. These are unsolicited applications.
The firm keeps a database of such applicants. When a vacancy arises, it screens the list and calls suitable persons.
This lowers the cost of recruiting as compared to other sources.
Step 3: Employment exchange:
Employment exchanges are set up by the government and keep a record of unemployed persons who have registered.
An employer tells the exchange of the vacancies and gets names of suitable persons.
They are a useful source for filling posts of skilled, unskilled and operative workers.
Step 4: Advertisement:
The firm publishes the details of the vacancy in newspapers, trade journals or on radio and television.
Advertisement reaches a very large number of people, so it gives a wide choice of candidates.
A drawback is that many unsuitable applications may come in, and the cost of the advertisement and screening can be high.
Final Answer:
Casual callers are unsolicited applicants kept on record, the employment exchange supplies registered job seekers, and advertisement gives wide publicity to a vacancy.