What is the meaning of the 'Bell of arms'?

A storeroom in which weapons are kept.

The correct answer is Option 2 - A storeroom in which weapons are kept.

The Bell of arms was a storeroom in which weapons were kept.

How the mutinies began:

The sepoys began their action with a signal:

1. In many places it was the firing of the evening gun or the sounding of the bugle.
2. They first seized the bell of arms and plundered the treasury.
3. They then attacked government buildings – the jail, treasury, telegraph office, record room, bungalows – burning all records.

Everything and everybody connected with the white man became a target. Proclamations in Hindi, Urdu and Persian were put up in the cities calling upon the population, both Hindus and Muslims, to unite, rise and exterminate the firangis.