Telephone cost monitor

A time use cost monitor for determining the cost of using a device for which time use costs accrue during use, said cost monitor comprising:

• an elapsed time clock for measuring time elapsing during use of the device, and generating a data signal corresponding to current measured elapsed time;
• data memory for storing data relating to both elapsed time and cost basis values;
• data entry apparatus for entering operating commands and cost basis values;
• a calculator for processing data corresponding to both elapsed time and to said cost basis values, and for deriving data corresponding to current accrued costs responsive to both data relating to elapsed time and data relating to cost basis values, and for generating a second data signal corresponding to said accrued costs, said calculator operating responsive to commands entered in said data entry apparatus;
• a display for displaying data relating to said elapsed time data signals and said second data signal corresponding to said accrued costs;
• and
• a power source for operating said monitor, comprising a battery and an on-off switch for conserving power of said battery, said data entry apparatus further including a reset key, for clearing said memory of data relating to current elapsed time and current accrued costs, and for resetting said memory to store new data relating to current accrued costs and current elapsed time,
• said data entry apparatus including
• a key for entering a command to display cumulative accrued costs,
• a key for entering a command to display cumulative elapsed time,
• an accumulator key for adding data corresponding to current elapsed time and to current accrued costs to data stored in said memory,
• an accumulator reset key for entering a command to clear said memory of cumulative accrued cost data and cumulative elapsed time, and for resetting said memory to store new data relating to cumulative accrued cost data and cumulative elapsed time, and
• an advisory key for entering, selectively, a command to signal completion of a predetermined time interval, and a command to signal attainment of a predetermined current accrued cost value, said elapsed time clock having means for generating a signal corresponding to completion of said predetermined time interval responsive to said command to signal completion of said predetermined time interval, and said calculator having means for generating a signal corresponding to attainment of said predetermined current accrued cost value responsive to said command to signal attainment of said predetermined current accrued cost value,
• said monitor further comprising an alarm responsive to signalling of completion of a predetermined time interval and to signalling of attainment of a predetermined current accrued cost value.