An adaptable programmable calculator is provided by employing a modular read-write and read-only memory unit capable of being expanded to provide the calculator with additional program and data storage functions oriented towards the environment of the user, a central processing unit capable of performing both serial binary and parallel binary-coded-decimal arithmetic, and an input-output control unit capable of bidirectionally transferring information between the memory or central processing uni...

A circuit is described which compensates for variation in the threshold voltage of Insulated Gate Field Effect Transistors (IGFETs) in an integrated circuit by modulating the substrate voltage in response to the variation of the threshold voltage from a desired nominal value.

A diffusion pump is provided in which an internal vacuum chamber is surrounded by regions of the pump through which working vapors flow. This configuration enables a single heating unit to heat both the working fluid of the pump and the vacuum chamber. In certain embodiments, a differential pump is provided in which a common boiler provides working fluid for a pair of pumping sections, each of which evacuates a different vacuum chamber. Application of this pump to a gas chromatograph/mass spectr...

A voltmeter having multiple voltage ranges comprises substantially linear elements such that the transfer functions of the elements can be independently measured and logically combined to derive the transfer function of a given combination of elements configured to obtain a given voltage range.

A hand-held, programmable, electronic calculator is capable of performing a larger number of functions than the number of keys on its keyboard and has one or more prefix keys to allow one function key to initiate more than one function. Each key generates a unique key code when it is depressed, and the calculator may be programmed by storing a series of the key codes in a memory. Memory space can be saved by generating unique merged codes to represent the combination of a prefix key and a functi...

A binary adder employs separate summing and carry circuitry within each digit to optimize the speed of operation of the adder. Carry bits of less significant digits are calculated independently of corresponding sum bits, thus allowing propagation of such carry bits to more significant digits before completion of the summation of the less significant digits.

A switching type power supply is provided which includes a first and a second SCR with a diode connected in reverse across each of them. The first SCR-diode pair in response to a clock pulse charges a capacitor which when fully charged causes the first SCR current to return to zero, forward biases the first diode and commutates the first SCR off for at least the required minimum turn-off time of the SCR. After the capacitor reaches the peak charge value, the second SCR is selectively triggered t...

A circuit for performing dual slope integration to provide a digital measurement of an input voltage of either positive or negative polarity employs a single source of reference potential in combination with a switchable resistive network as a source of reference current.

Wrist wearable straps and a case are disclosed, each having an interior cavity for engagedly storing a special tool. One wrist device strap is made of a selected material and defines a pocket for holding the special tool. A second wrist device strap includes at least one special link defining an interior cavity for holding the special tool. These special links also include a removable portion to which is attached a special tool. The removable portion blends with the remainder of the link to give...

An adaptable programmable calculator is provided by employing a modular read-write and read-only memory unit capable of being expanded to provide the calculator with additional program and data storage functions oriented towards the environment of the user, a central processing unit capable of performing both serial binary and parallel binary-coded-decimal arithmetic, and an input-output control unit capable of bidirectionally transferring information between the memory or central processing uni...