3. 301 TELEPULSE CODING UNIT General Description In the Telepulse Coding Unit, (Figure. 12) the ground level radiation intensity from the detector is measured by vacuum tube voltmeter bridge which drives a strip chart recorder and is also converted to a periodic, time-modulated, constant-amplitude pulsetrain for radio transmission. This type of signal is suitable for transmission by both telephone lines and radio. The instrument is powered by 115 volts at 60 cyoles. An auxiliary unit, the Junction Box, contains a control to permit either voice communication or telemetering over the plane radio tranamitter. 3.2 Circuit Description The Unit is divided into four subsections: 3) Comparator, and 4) Power Supply. 1) Bridge, 2) Converter, The circuit diagram is shown in Figure 13. 302.1 Bridge In the bridge section, the ground level radiation signal from the detector is emplified by a balanced D.C. amplifier, V-1 (a one volt full soale sensitivity). It drives a strip chart recorder (Esterline- Angus Model AW) end the meter on the control box of the "Top Hat" airborne detector, The radiation intensity corresponding to the current indicated it can be obtained from the calibration curves given in Figure 5 or three decade chart paper (Esterline Angus type 1273) may be used and the intensity read off directly. = 27 = The voltage