1-2. The Model 4270A is a programmable, bipolar dc voltage source and.ac power amplifier. Output voltage is from 0 to ±1 lOVdc in two ranges, 10 and XIOVdc. Programming resolution using the internal reference voltage is lmV on the 10 volt range and 10mV on the X10 volt range. Output accuracy is given in paragraph 1-6. After a IQQßs settling time, a READY flag indicates that the output has settled to ±0.01% of the programmed level for a resistive load. The output current is rated at ±0.5 ampere maximum and is limited to approximately ±0.6 ampere in the event of an overload or short circuit. The sink current (milliamps) is rated at 500--4.5E OUT maximum. A Programmable Current Limiter (Option —06) is available to allow programming the maximum output current to a lower level. A current limit flag indicates when a sink or source current overload exists with or without the —06 Option. 1-3. Programming requirements are compatible with DTL or TTL logic levels. Contact or relay closures can also be used. The voltage source is programmable using BCD or binary-per-decade coding, using 84-2-1 format. All programming inputs and flag outputs are made through a 50- pin Amphenol, Blue Ribbon connector located on the rear panel. A +5Vdc output is also available at this connector and is used to provide power for external programming circuitry. Negative logic is employed for programming. The logic levels are as follows: Logic “0” = +2.0Vdc to +5 .OVdc or open circuit. Logic “1 ” = 0 to +0.4Vdc or short circuit to LOGIC GND. 14. Four options are available and provide tailoring of the power supply to fit application requirements. These options are identified by numeric designations —03, —06, —07, and —09. Each option is described in Table 1-1. The options can be installed at the factory when the instrument is ordered or in the field at a later time. 1-5. This power source is completely solid state. Plugin printed circuit boards, with accessible test points and adjustments, are provided for ease in servicing. The unit is forced-air cooled. This results in lower component temperatures and higher reliability than would normally be obtained in a source of this power capability. The chassis is designed for bench top use, or it can be installed in a standard equipment rack by using the Accessory Rack Mounting Fixtures.