Abstract: An improved instrument for preparing quality control solutions of liquid and gas for use in calibrating blood gas analyzers includes a gas inlet providing gas to a humidifier, a diffusion tube, flexible tubing connecting the gas from the humidifier to the diffusion tube and a temperature controlled environment for the diffusion tube. These standard components are arranged in a unique combination permitting the tubing connecting the outlet of the humidifier to the diffusion tube and the diffusion tube itself to both be replaced or individually replaced without disturbing the other components of the instrument. For this purpose, a metal heat block is used as the temperature controlled environment and is provided with an open top for receiving the diffusion tube. The humidifier and connecting tubing are exterior of the heat block so that the referred to replacement of the tubing can readily be carried out.

Abstract: A push-button keyboard is located on the dashboard of a truck for unlocking a rear access door to rear cargo space in the truck. Selected ones of the keys are sequentially operated in accord with a given combination generating a signal which throws a lock bolt as by means of a solenoid. A first timer prevents operation of the lock unless the combination keys are operated within a first given time interval. A second timer automatically releases the solenoid operated lock bolt after a second given interval of time has elapsed to relock the access door in the event it has not been opened. The signal to the solenoid operated bolt itself is frequency coded to inhibit introduction of unauthorized signals in an unauthorized attempt to operate the lock.