(1 + c)/(r + e + c). The money multiplier (also called the credit multiplier or the deposit multiplier) is a measure of the extent to which the creation of money in the banking system causes the growth in the money supply to exceed growth in the monetary base.
A buzzing light switch could mean the fixture is wearing out, causing an arc of electricity behind the wall plate. If this is the case, the potential for an electrical fire may exist.
Think of it like a light bulb: when the light switch is on, a circuit is formed and the bulb shines brightly. When the switch is turned off - or, in the case of a fire protection tamper switch, the valve closes - the circuit is broken. For tamper switches, this broken circuit creates a signal.