Main article: Receiving tubes have heaters or filaments intended for direct battery operation, parallel operation off a dedicated winding on a supply transformer, or series string operation on transformer-less sets. High-power are directly heated; the heater voltage must be much smaller than the signal voltage on the grid and is therefore in the 5.25 V range, drawing up to hundreds of amperes from a suitable heater transformer. In some valve part number series, the voltage class of the heater is given in the part number, and a similar valve might be available with several different heater voltage ratings.

Tube bases and envelopes [ ]. Main article: Abbreviations used in this list [ ] • ST – Shouldered tube • GT – Glass tube • MT – Miniature tube, such as or • FL – Subminiature all-glass elliptical body and flat bases with long, inline 'flying leads' (pigtails) that are soldered into the circuit • SL – Subminiature all-glass elliptical body and flat bases with short inline leads that can be soldered or can be mated with a special socket. (Flying leads can be cut short to fit into inline sockets.) • R8 – Subminiature all-glass round body and base with 8 flying leads or stiff pins arranged in a circle Numbering systems [ ] North American systems [ ] RMA system (1942) [ ].

Because the card punch limits the number of availa. 6P3S-'fE BEA SIN. 20 lhA 40A 100. 20 3hA 85A 100. Glass bulb or metal anode (power tubes) in eighths of an inch according to the American. Neon-argon gas-filled. Neon gas-filled. Mercury vapor-filled. 6P3S-YE BEA SIN.

Main article: The system assigned numbers with the base form '1A21', and is therefore also referred to as the '1A21 system'. Main article: RETMA is the acronym for the Radio Electronic Television Manufacturers Association formed in 1953. • The first character group is a number representing the heater voltage rounded to the nearest whole number; 0 indicates a. • One or two letters assigned to the devices in order of development. • A single numeral that represents the number of active elements in the tube.

Tip In the stock market, UNCH means that the stock's price for the trading day has remained 'unchanged.' Volatility of Thinly Traded Stocks Some popular stocks, such as Apple, may trade tens of millions of shares per day. Others may not trade a single share. Stocks that don't trade at all will end up unchanged for the day. A stock that doesn't trade many shares per day is said to be thinly traded. In and of itself, this isn't necessarily a bad thing. However, thinly traded stocks are notoriously volatile.

This may be counterintuitive; after all, how can a stock that ends the day UNCH after trading zero shares be volatile? The truth is that a thinly traded stock that is UNCH one day may be up or down 10 percent, 20 percent or even more the next day. The day after, it might not trade at all again and finish UNCH. Bid-Ask Spreads The other danger with thinly traded stocks is that the bid-ask spread is normally large. The bid-ask spread represents the combination of the highest price that a buyer will pay (the bid price) and the lowest price a seller is willing to sell (the ask price). A large bid-ask spread represents a profit margin for the specialist or market maker who conducts the actual trade of a stock. When you pay a large bid-ask spread, your trade costs you more money.

For example, imagine that a stock has a bid price of $50 per share and an ask price of $52 per share. If you buy the stock at $52, you're essentially paying $2 more than the true value of the stock, as determined by the price at which you can sell it. Random Walk Theory Many investors are familiar with the book 'A Random Walk Down Wall Street,' written by Burton Malkiel in 1973. The book presents many investment concepts but essentially proposes that stock price movements are random and unpredictable. Although trends may be identified, Malkiel suggests that moment-to-moment stock price changes cannot be determined with any accuracy.

And so it goes with stocks that end up UNCH on a day. Even a stock as actively traded as Apple may end up UNCH on any given day, and that cannot be predicted with any accuracy. The stock may go up in the morning, come down in the afternoon and finish back at UNCH, or it may simply hang around either side of UNCH and just reach UNCH on its final tick. In this case, there may not be any 'meaning' at all in the fact that the stock closed at UNCH; it was just another random walk.

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