7412532936

90-WATT CW TRANSMITTER* #720 Kit $79.95    Wircd $119.95

•■Ideał for weteran or nowice" - ELECTRONIC KITS CUIOE. "Top quality" - POPULAR ELECTRONICS. "Weil designed"- ELECTRONICS W0RLO. 80 (hru 10 meters with one-knob band-switchmg. Fuli "dean” 90W input, 6SW ex-ternal piąte mod. Matches loads SO to 1000 ohms. May be used as basie eiciter unit. TVI shielded. Tubes: 6146. 6CL6. 2-6A05. GZ34 Attractive "living room” low-silhouette design. 15" w, 5- h, 9“ d.

UNIVERSAL MODULATOR-ORIVER #730 Kit $49.95 Wircd $79.95 Covcr E-5

Oeliwers 50W undistorted audio. Modulates transmitters havmR r.f. inputs up to 100W. Umque over-modulation indicator. Output transformer matches 500-10.000 ohms. Low-lewci speech clippmg & filtering. Inputs for xlal or dynamie mihes. phone patch, etc. 7 tubes. 6- h. 14- w. 8- d.

GRID DIP METER

Kit $29.95 Wircd $49.95 #710

_ includes compiete set of coils for 2 fuli band coweroge. 400 kc-230 mc in « 8 overiapping ranges. 500 ua meter.

« Piugin coils are pre-wound, pre-caiibrated to i 0.5% accuracy. Translormer operjted power £ supply. 2V«" h. 2'aS w. V/%" I.

tiC Comparc—judge for >oursclf-a( your ncigh-q borhood EICO disiribuior. For frcc caralog o on 65 modlił of EICO cesc imiruments. hi-fi “ jk “ham" gear. liii ouc coupon on Pagc 36

(UCTtOHiC inSIRUMfni CO. I«tc

3300 N IM. t I C l. » I.

O 1059

io the solar ccii. The output of tlic photocell is ampłified by a tiansistor amplifier. which. in turn, aeluates an alarm light.

The instrument consists of a dc-tector, containing the platinum fila-ment, and the amplificr-alarm. con-laining the transistor circuitry and indicator lamps. The dctectoi* is in-stalled in the bilges or engine com-

unit. .This momentarily places a higher-than-usual \oltagc across the sensing filament. artificially duplicating the presence of gasoline fumes. This trig-gers the alarm proving that the gas detector is on the job and wotking projierly. With older units it was necessary to e.\pose them to fumes from gasoline-soaked rags in order to chcck their operation.    -{SÓ-

The automalic gas alarm employs a solar celi to pick up inlrared energy g'»ven oH by a platinum wire when gas iumes are present. The solar cell’s signal goes to a transistor amplifier. This closes the alarm Circuit (dashed lino) and ilashes the red alarm light on the instrument panel. In the standby condition the cur-rent flows through the solid-line Circuit. During test, additional power is ap-plied to Ihe platinum wire causing it to emit inlrared energy and trigger the alarm Circuit. Conventional gas alarms are based on the Wheatstone-bridge prin-ciple. Here a carefully balanced Circuit produces no current ilow in the normal condition. When gas iumes reach the exposed platinum filament. it overheats and expands changing its electrical resistance and upsetting the balance of the bridge. The unbalance causes current to flow from the bridge to operate a meter or light.

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