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Friden 1160/1162 Circuit Board #3
Board #3 is used both in the Friden 1160 and 1162 calculators. The circuit board contains primarily the arithmetic logic unit (ALU) of the calculator. The circuitry is the essence of what allows the calculator to perform the basic counting operations involved in performing the math operations provided by the calculator, as well as also providing for transfer of data between the three counters used in the ALU. The Friden 1166 uses a different version of Board #3, but still utilizes the same custom ICs as the 1160/1162 version of the board, but is not interchangeable with the 1160/1162 board.
Board #3 contains three custom bipolar TTL integrated circuits manufactured by Texas Instruments (see the exhibit on the Friden 1162 for information concerning discovery of an exception to TI's manufacture of these devices) for Singer/Friden. These three devices mimic the functionality of each of the three switch-tail ring counters used in the transistorized first-generation Friden 130 /132 "three counter" calculators. The devices have part numbers SN1286(A Counter), SN1287(C Counter), and SN1288(D Counter), and are packaged in 24-pin dual-inline plastic packages.
The board contains a total of 26 integrated circuits, mostly DTL devices, with two 7400-series TTL ICs(one 7400 Quad 2-Input NAND gate, and one 7476 Dual J-K Flip Flop), and the three TTL custom counter chips. Along with the ICs, there are 15 diodes and four resistors.