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The Field Monitoring System described here is being used for long-term measurements of radiation dose rate in the vicinity of nuclear reactors. The output of a high pressure ionization chamber is converted to a binary number, which is written on a magnetic tape cassette every ten seconds. The digital recording permits direct entry of the data into a computer for analysis. The instrument is powered by a rechargeable plug-in battery pack. This permits complete flexibility in choice of monitoring sites. Through the extensive use of COSMOS integrated circuits, a modest sized battery pack yields 18 days operation.

An underwater acoustic telemetry system was developed to provide a two-way communications link between an ocean-bottom seismograph and a ship overhead. Four data channels are transmitted from the instrument on IRIG Channel 12 (10.5 kc/s). Commands to the instrument are transmitted in the form of a simple pulse position code using a 14 kc/s carrier, and provide for such functions as gain change, calibration, instrument leveling, and uncaging. A mercury battery pack provides sufficient power for 15 days of continuous operation. Acoustic power output is approximately 2.5 watts at an overall efficiency of 20 percent. Instrumentation and batteries are housed in two spherical pressure vessels designed to withstand depths in excess of 2500 fathoms. The system was successfully operated in May, 1964, off Bermuda.

One kerosene oil-fuelled thermoelectric generator of maximum power capacity of 2·2 W. d.c. has been designed and constructed with ZnSb and constantan elements for powering A.I.R. community receiver requiring about 2·0 W. d.c. for maximum useful output from the receiver. The receiver generally operates from a 9 V. dry battery pack, which is costly and having limited self life and irregular supply. Whereas, the generator works on cheap fuel readily available even in remote villages, its running cost is practically nil with kerosene lamp supplying normal light at night and is about 10 np/hour with wick-stove and is having very long life. Some design aspects and the cost estimation of the generator are also presented in the paper.

A simple battery‐operated survey instrument has been developed which uses a photo‐multiplier tube to detect the scintillations produced in a phosphor by α‐particles. The electrical components are a 1100‐volt battery pack; a 931A photo‐multiplier tube; a matching transformer and headphones for registering single particles; and a crystal rectifier, choke, and meter for use with strong sources. The latter group of components are used in a novel ``charge‐multiplying'' circuit which increases the meter sensitivity by a factor of 12. The instrument is insensitive to β‐ and γ‐radiations.

The Army Concept Team in Vietnam evaluated the Tunnel/Cache Detector - Portable Differential Magnetometer (PDM) to determine its suitability as a tunnel and cache locator in the combat environment of Vietnam. The PDM consists of three subsystems - a sensor and staff assembly, an audio readout, and a rechargeable battery pack. The complete system also includes manuals, spare battery pack, battery charger, spare cables, earphones, and target recording materials. Total weight of the system including the 60-pound storage case was 106 pounds. The 1st Cavalry Division (Airmobile), the 25th Infantry Division, and 3d Brigade, 9th Infantry Division operated seven PDM from 25 March to 25 May 1970. The PDM provided a limited capability to detect and trace tunnels and to detect caches. It was recommended that the PDM not be deployed to Vietnam and that future development efforts on tunnel and cache detection equipment be directed toward light weight and rugged equipment that can operate effectively in dense vegetation.

The Porta-Prompter consists of a sound-shielded microphone, amplifier, switching circuits and battery pack built into a pint volume polyethylene shell. Four miniature earphones can be used by a therapist or trainer to communicate with up to four clients or students. Prompts and verbal feedback can be given to guide subjects' performance without interfering with ongoing social interaction. The porta-Prompter can be used to teach interactional skills in family therapy, in group assertion training, and in professional training programs.

Design has been completed for a rocket probe system which will determine air density at altitudes of 70 to 130 km. The design differs from that of similar probes presently being used for obtaining density measurements primarily in the signal processing electronics. It employs a digital processor which encodes 50 complete acceleration readings per second and generates a PCM output signal whereas previous probes have been analog in nature and have made use either of a multisubcarrier FM-FM system or a commutated signal subcarrier FM-FM system. In order to confirm the validity of the electrical design, a prototype unit has been fabricated and bench tested. Temperature tests have been performed on the prototype unit and indicate that over a 0 to 60C temperature range, an accuracy figure of plus or minus 0.1 percent has been achieved for the signal processing electronics portion of the probe system. This represents an order of magnitude improvement in accuracy over a typical FM- FM system. Power for the system is supplied by an internal battery pack consisting of seven rechargeable nickel-cadmium cells which have a capacity sufficient to operate the probe system for a duration of 40 minutes at room temperature.

TRANSMITTERFigure 1. Transmissometer AssemblyDEEP SEA OPTICAL TRANSMISSOMETERHerman K. Ruhlmann and Louis J. Free U. S. Navy Underwater Sound Laboratory Fort Trumbull, New London, Conn. 06320AbstractThe requirement for an accurate optical profile of the sea from the surface to 6500meters initiated the design and construction of the Navy Underwater Sound Laboratory's deep sea trans- missometer. The instrument is a 4-meter, single- path, non-collimated, optical transmissometer capable of transmitting data to the surface by cable or automatically recording it in a self- contained package. This paper describes the design, construction, and calibration of the transmissometer and the data obtained in the North Atlantic Ocean to depths of 5100 meters.IntroductionThe Underwater Sound Laboratory's 4-meter transmissometer was designed and constructed to measure the optical transmittance of the sea to a depth of 12,000 meters in order to increase our knowledge of the optical properties of the deep ocean.As conceived, the system was required to have the following capabilities:1. Ability to measure accurately the trans- missivity of very clear sea water.2. Simplicity of operation.3. Non-critical optical alignment.4. Insensitivity to ambient light.5. Insensitivity to water temperature changes.6. Ability to withstand normal handling aboard ship at sea without loss of calibration.7. Battery powered operation.8. Signal stability for up to 6-hour periods.The final design consisted of a series of trade-offs in order that these requirements could be satisfied most completely.Transmissometer DesignThe transmissometer (see Figure 1) consists of a mounting frame 6 meters long, on which are mounted four pressureproof housings. These hous­ ings contain the receiver, recorder, transmitter, and battery pack. The housings for all but the recorder are standard E G and G housings capable of withstanding depths of 12,000 meters. The recorder housing, designed and fabricated at USL, presently limits the depth capability of the system to 7,000 meters.RECEIVERRECORDER PACKAGEBATTERY PACK Figure 1. Transmissometer Assembly

A self-contained positive pressure air supply respirator unit is described which can be used with all types of continuous flow supplied air facepieces. Air demand for the wearer is supplied from the exposure environment through an air purification package consisting of a DC motor, air mover, rechargeable battery pack, and air purification element. The air mover is a miniature, positive displacement, Roots type blower delivering 4.0 CFM at a total head of 2″ H2O. The air supply package weighs approximately three pounds and can be conveniently worn on a belt harness. Performance tests under moderate work conditions showed leakages of less than 0.10% for the three-hour life of the unit.

Problems involved in developing a long-life FM telemetry transmitter for tagging small mammals are described.