# Can't identify these elements in this schematic

could anyone help me identify these elements I have highlighted in red in this schematic? I'm trying to learn how to read schematics and am making a lot of progress but since this document is from the 70s early 80s it uses some non standard symbols.

• They are all pretty standard symbols though. – Asmyldof Oct 10 '16 at 7:59
• It's part of the bass pipes of an electronic organ, isn't it? – Brian Drummond Oct 10 '16 at 10:43

The N.C refers to "Not Connected". You may wonder why the emitter of Q1 is connected to a voltage divider (R10/R11) when the base and collector are not connected to anything. Q1 is part of a CA3046 transistor array and the emitter of Q1 is also the substrate for the chip. It should be connected to a point with a relatively negative potential.

The 8 dots and wide black shorting bars (that short two pair of pins in one of three positions) is a 2 pole 3 position slide switch..

The '0.00V' indicates the voltage at that node of the circuit- it is a virtual ground since U2A drives the long-tailed pair to force that node to 0.00V.

-12V is a supply rail, as is +12V.

The arrow is the wiper of a 500$\Omega$ trimpot, used to adjust the voltage very slightly- it's nominally about 0.63V, so very similar to the voltage on the base of Q5. However it is fixed, and the voltage on the base of Q5 will drop by 2mV/degree C of the CA3046 die temperature. The purpose of this is to ovenize the CA3046 (maintain an elevated constant die temperature). To this end, Q4 is used to heat the die, and Q5 is the temperature sensor with Q6 and U2B forming a feedback controller. If you don't have details of the adjustment procedure I would suggest not messing with Mr. trimpot.

In this circuit schematic,

1. NC : Here, NC stands for Not Connected i.e. floating terminal/connection
2. SW1 is sliding switch
3. 0.00V : Potential on the wire on that point
4. R14 : Arrow at R14 indicates that the resistor is variable. i.e. it is a potentiometer with maximum resistance of 500 (unit is not visible due to red marking on image)
5. -12 : It is negative power supply of magnitude 12V. There are power supplies available with negative and positive voltages with three terminals like +12V, GND, -12V. Voltage across -12V and GND is -12V which is given to the terminal shown in your circuit diagram.
• No unit on R14 so 500 ohm. R14 is not the only potmeter. Also R3 and R7 . – Decapod Oct 10 '16 at 8:02