The A and M series blasting machines are housed in black metal cases.
Each has a small crank, an indicator lamp and two condenser terminals.
As the crank is turned, the direct current generator charges a condenser.
When the required voltage is reached, the indicator lamp glows.
By turning the crank a few more times the condenser discharges and fires the electric caps in the blasting circuit.
If the lamp does not darken after the additional crank turns, a short or break in the demolition circuit is indicated.
The A 5106 and M504 are manufactured with various capacities.