Electric Fittings for Speaker Extensions.

Radio Record, Volume II, Issue 16, 2 November 1928, Page 29

Electric Fittings for Speaker Extensions.

. HERE an output filter or transformer follows the receiver and polarity of connection to the speaker is immaterial, electric light fittings form a very handy system for connecting up speaker leads and extensions, and for the latter ordinary lighting extensions may be pressed into use at any time. There is one point to note, which is that the lamp socket should be attached to the speaker cord, so that it is impossible for anybody to

connect the speaker to the lighting system "just to see what it would do." An adapter plug with short leads connects to the set. Extensions or speakers are then rapidly connected with minimum effort. Fuses for Filament Protection. With the low consumption filament of many modern valves the use of a small torch bulb as a protective fuse in the B negative lead is not safe, owing to the relatively high consumption" of the bulb’s filament. A

safe method of use is to crack the glass of the bulb, which allows air to enter, and greatly lowers the fusing: point of the filament. The use of 4 fine strip of lead tinfoil is cheap and very reliable as a protective fuse. It -is wiser to have some kind of fuse in B negative than risk handing out the price of three or four re-place valves. Regulations Concerning Mains Connections, _ LONDON radio journal of recent date contains new regulations specially framed to cover the use of wireless apparatus connected to the mains. The chief provisions are protection of all terminals from = accidental contact, metal cases connected

to earth, fuses on both poles of input, earthing of certain receivers only through high-test condensers. All "mains" transformers to be doublewound (which means no auto-trans-formers), adequate insulation of 1000 volts a.c, test between windings, and high insulation from the mains input » terminals. . Care of A Batteries. {tz is important for long battery life to re-charge when the battery is 80 per cent. run down. Always keeping a batter "well up’ means long life. « If an accidental "short? occurs it will not be harmful if the temperature does. not exceed 100 to 110 deg. F., and if the battery is put on charge at once. ln