during the course of a program execution following the block 334 is a block 336 which resets the value stored in the beepo timer which as before noted stores the delay period between consecutive audible sequences if the block 330 determines that the beepl timer has been decremented to zero then a block 338 checks the value stored in the beepo timer to determine whether it has expired if not a block 340 decrements the value stored therein if the beepo timer has expired control passes to the block 322 control from any of the blocks 322 336 or 340 returns to block 124 in the main program fig7 referring now to fig1 a 13b and 13c the test subroutine is illustrated in detail a block 327 determines whether the test mode has been selected by reading the input in1 if the status of this input indicates that the auto scan switch 66 is not in the reset position then a series of blocks 329 335 reinitialize the check condenser timer ccond if the check condenser flag ccfg is set and reset the flag flshfg and set the flag prfg control from the block 335 then passes directly to the block 128 which resets the test mode initiate delay timer test d the control program then resumes cycling through the various subroutines in the normal mode if the block 327 determines that the test switch is in the reset position then a block 339 reads the contents of the test mode initiate delay timer test d to determine whether it has expired as previously mentioned the test d register is initialized at a value of two seconds and hence the test mode functions do not occur until this initial delay has elapsed this.