counter 41 which receives 720 input signals for each output signal generated the output signal from the 12 hour counter 41 is supplied to a monostable circuit 42 which when triggered from its stable condition provides a signal until the circuit reverts to its stable condition or state circuits of this type are well known and rely on the product of resistors and capacitors to determine the duration of the output signal an adjustable resistor 43 is shown connected to the monostable circuit block to indicate that the duration of the output signal is adjustable by the operator also a manual reset 44 is provided to permit independent triggering of the monostable circuit and the initiation of an output signal therefrom at the control of the operator thus either a signal from the 12 hour counter 41 or an operator generated reset signal from the manual reset 44 will cause with monostable circuit to provide an output signal the duration of which is determined by adjustment of resistor 43 this pulse signal is shown in fig3 as commencing at time t1 and terminating at time t2 the pulse output signal of the monostable circuit 42 is provided to temperature sensor 50 and level sensor 51 the level sensor discussed in connection with fig2 will appear as an open circuit if the fluid within container 18 does not cover the exposed wire ends 31 the open circuit condition of the level sensor will also trigger an audible alarm 52 to alert the user that a new container of fluid must be prepared for use a temperature sensor 50 is preferably employed with the installation and is connected to a temperature sensor located within the drainpipe 12 the determination that the temperature within the drainpipe 12 is outside.