Location Tenierstraat-Pieter de Hoochstraat was opened in 1911 to provide connectivity to new subscribers in the southern parts of the city (this area was rapidly growing at the time). To distinguish from the Spuistraat exchange, this office was known as Zuid (South). Initially a S&H semi-automatic office for 1500 subscribers, gradual capacity improvements lead to a 10000 lines office in 1920. In 1925, this office was converted into automatic service serving the 2XXXX range. A second automatic exchange was added in 1931 for 2000 lines and later extended to 6000 lines in 1936 serving the 9XXXX range.

Location Singel 340 was opened in 1921 serving the same area as the Spuistraat exchange, but baptised Centrum. Initially supporting a semi-automatic office for 6000 lines served from a temporary exchange at Spuistraat, from 1922 onwards home to an automatic exchange for 8000 lines in the 3XXXX range.

Location Middenweg in the Watergraafsmeer was opened in 1924 as a semi-automatic office for 4000 lines. After conversion to automatic service, it served the 5XXXX range. In 1935, capacity was increased to 5000 lines.

Location Wingerdweg was opened in 1925 for serving 1000 lines in the area north of the river Y. It was a semi-automatic sub-exchange tied to the Noord-exchange, meaning that operators would be handling calls at the Noord exchange. After converting to automatic service, this exchange served the 6XXXX range.

Location Ph. van Almondestraat opened in 1928 on the West side. This exchange was initially serving 4000 lines, later in 1930 upgraded to support 6000 lines.

District Amsterdam in 1974	District Amsterdam in 1983

District Amsterdam (1973-1983)
After WWII, new offices were needed in a circle around the inner-town due to a steady increase in new-built areas to home the baby-boom generation. Simultaneously, demand for residential telephony service was exploding. The original sites Z, C, O, N, W were complemented with new exchanges Kad, Slod, Slom, Slov, Btv, Blm as shown on the right, to provide services in Kadoelen, Sloterdijk, Slotermeer, Slotervaart, Buitenveldert and Bijlmer.
The left map shows a projection of PTT Telecom's telephone exchanges in greater Amsterdam in 1974. In those days, the services offering was limited to telephony, and the exchange buildings would accomodate one or more, large electro-mechanical, electronic or early stored-program control switches. The local loop (i.e. wires between subscriber and telephone exchange) would connect to the site's Main Distribution Frame (MDF). The right map shows the same area ten years later, in 1983, with not much having changed.
The area enclosed by the dotted line around Amsterdam was called a sector. Within the sector, circles depict 'local' offices (serving local subscribers). The dark boxes depict the 'district' offices that interconnect the local offices within the sector as well as 'knooppunt' offices of nearby sectors. The latter office type is a round solid circle like is shown in Purmerend and serves traffic between local offices within the sector, and serves any traffic with another sector through connections with the nearby district exchange. In Amsterdam, de 'knooppunt' office was integrated in the 'district' office.

Decibel Re-numbering Operation (1990s)
Due to the availability of computer technology in the telephone exchanges, consolidation of the numbering plan became possible as of the mid-1990s. In 1996 the last electro-mechanical switch in the Netherlands was phased out (Kesteren).
Until the mid '90s, the Netherlands would have an open numbering plan with variable number lengths in use. Local subscriber numbers would be 3 through 7 digits long, and these could be dialed without any prefix if dialed within the same numbering area code. Within an area code, usually a single length subscriber number would be defined, although in central Amsterdam both 020+5 digits and 020+6 digits were co-existing.
Area codes would be in the format 0SABC or 0SA, with 0 being a toll selection prefix that would be skipped if dialed from outside the Netherlands (country code 31 followed by area code SA.. digits).
Government altered the telephony numbering plan in the Netherlands mid '90s to allow for (1) uniform 10-digit number length throughout the country (2) less area codes and different tariffing zones by consolidating 5-digit codes into 4 digit codes (0SAB). PTT named this operation 'Decibel', and for a short while both old and new numbering plan where simultaneously supported.
The area code assignment within the Amsterdam District was changed as follows:

former	sector	current
area code		area code
020	Amsterdam Central	020
0290X	Amsterdam North East	020
0294X	Weesp	0294
0296X	Ouderkerk	020
0297X	Randwijck	0297
0298X	near Zaandam	075
0299X	Purmerend	0299
075	Zaandam	075

MDF locations in Sector Amsterdam (area code 020) (2004)
The thumbnails below depict MDF locations in the Amsterdam sector, currently serving the 020 area codes. Each site is clickable to provide a 640-pixel photo, as well as data like address and the pre-Decibel area code during the early 90's. You can also refer to a pre-1995 document found on the WWW that holds all MDF sites at that time reference [7]. If you think taking pictures of telecom's buildings is weird - check out this site by Roger Hünen: KPN exchanges in Limburg, Netherlands.

asd-asv	asd-bdh	asd-blm	asd-btn	asd-btv	asd-c	asd-dim
asd-kad	asd-n	asd-o	asd-ohg	asd-osdp	asd-rwck	asd-rzbg
asd-slod	asd-slom	asd-slov	asd-slw	asd-spl	asd-w	asd-ijb
asd-z	biw	htrk	ip	lm	odk	znb

MDF locations in adjacent sectors (area codes 0294, 0297, 0299, 075) (2004)
Sites Oost Knollendam (02982) and Wijdewormer depicted on the overview maps are no longer in service and are not included.

asmr	hf	mdt	naa	uh	vin	abc
baa	ln	mdn	nhorst	wp-c	as	as-sndt
ozn	wgd	wor	wor?	zd-c	zd-wm	edm-c
edm-vldm	edm-?	kdk	mrk	midb	mn	noo
oh	pm-c	pm-pmr	rp

Transit exchange buildings in greater Amsterdam (2004)
In addition to MDF sites that may or may not host an actual telephone exchange for providing local services, there are other sites that are in use by the telephony operators for providing their telecommunications services. For instance, in order to route telephone traffic from local offices to other destinations, transit exchanges may be used. Usually the existence of transit exchanges is invisible and transparent to the network user. However, in the greater Amsterdam area the regulator has forced the incumbent operator to provide internetwork connectivity through a Regional Access Point transit exchange in Buitenveldert (see reference [4]). Previously, a transit exchange was called 'knooppuntcentrale (KC)' or a 'districtcentrale (DC)'. Details about their locations may be found through indirect sources, like reference [5].

asd-dcI

asd-dcII

asd-dcIII

Coda
As an example, the local exchange the author's home phone connects to is an L.M. Ericsson AXE exchange that is on the site referred to as 'ASD-DIM' (below the S of Amsterdam on the map). This site has at least 3 local exchanges because the operator (KPN) provides regulatory interconnection on all 3 exchanges as can be found in publicly available information like reference [3]. The site provides ADSL access to the major Dutch DSL providers as is shown in reference [2].

References

[1] Van Hemert, Kuin, "Automatische Telefonie", Vereniging van Technisch Hoger Personeel der PTT, zesde druk, 1970.
[2] WWW snapshot, "http://www1.oli.tudelft.nl/adsl/all.cfm", availability of ADSL on MDF locations.
[3] WWW snapshot, "https://www.kpn-wholesale.com/content/doc/Table_3_Local_Access_Point_Locations.xls", availability of Host Access on KPN local exchanges.
[4] WWW snapshot, "https://www.kpn-wholesale.com/content/doc/Table_2_Regional_Access_Points.doc", availability of Regional Access on KPN trunk exchanges.
[5] WWW http://www.schwenckerosbach.nl/eng/presentation/projects/h3.html, AGS Schwencke Rosbach Architects project overview.
[6] Gedenkboek Gemeente Telefoon Amsterdam, 1896-1936, published 1936.
[7] WWW snapshot, "http://a-domani.nl/kpn_info.html", list with all KPN sites (date unknown, must be pre-1995).