Housing and Development Board

The Housing & Development Board (Abbreviation: HDB; Malay: Lembaga Pembangunan dan Perumahan; Chinese: 建屋发展局; pinyin: Jiànwū Fāzhǎn Jú; Tamil: வீடமைப்பு வளர்ச்சிக் கழகம்) is the statutory board of the Ministry of National Development responsible for public housing in Singapore. It is generally credited with clearing the squatters and slums of the 1960s and resettling residents into low-cost state-built housing. Today, as many as 82% of Singaporeans live in public housing provided by the HDB.

History

Shortly after achieving self-governance in 1959, Singapore faced a serious problem of housing shortages; low construction rates and massive damage from World War II further exacerbated the prewar housing shortage. In 1947, the British Housing Committee Report noted Singapore had "one of the world’s worst slums -- 'a disgrace to a civilised community'", and the average person-per-building density was 18.2 by 1947. High-rise buildings were also rare. In 1959, the shortage problem remained. An HDB paper estimated that in 1966, 300,000 people lived in squatter settlements in the suburbs and 250,000 lived in squalid shophouses in the Central Area. In its election campaign in 1959, the People's Action Party (PAP) recognized that housing required urgent attention and pledged to provide low-cost housing for the poor if it was elected. When it won the elections and formed the newly elected government, it took immediate action to solve the housing shortage. The government passed the Housing & Development Act of 1960, which replaced the existing Singapore Improvement Trust with the Housing & Development Board.

VGA connector

A Video Graphics Array (VGA) connector is a three-row 15-pin DE-15 connector. The 15-pin VGA connector is found on many video cards, computer monitors, and high definition television sets. On laptop computers or other small devices, a mini-VGA port is sometimes used in place of the full-sized VGA connector.

DE-15 has been conventionally referred to ambiguously as D-sub 15, incorrectly as DB-15 and often as HD-15 (High Density, to distinguish it from the older and less flexible DE-9 connector used on old VGA cards, which has the same E shell size but only two rows of pins).

VGA connectors and cables carry analog component RGBHV (red, green, blue, horizontal sync, vertical sync) video signals, and VESA Display Data Channel (VESA DDC) data. In the original version of DE-15 pinout, one pin was keyed by plugging the female connector hole; this prevented non-VGA 15 pin cables from being plugged into a VGA socket. Four pins carried Monitor ID bits which were rarely used; VESA DDC redefined some of these pins and replaced the key pin with +5 V DC power supply.

Modified AMI code

Modified AMI codes are Alternate Mark Inversion (AMI) line codes in which bipolar violations may be deliberately inserted to maintain system synchronization. There are several types of modified AMI codes, used in various T-carrier and E-carrier systems.

Overview

The clock rate of an incoming T-carrier is extracted from its bipolar line code. Each signal transition provides an opportunity for the receiver to see the transmitter's clock. The AMI code guarantees that transitions are always present before and after each mark (1 bit), but are missing between adjacent spaces (0 bits). To prevent loss of synchronization when a long string of zeros is present in the payload, deliberate bipolar violations are inserted into the line code, to create a sufficient number of transitions to maintain synchronization; this is a form of run length limited coding. The receive terminal equipment recognizes the bipolar violations and removes from the user data the marks attributable to the bipolar violations.