SWEDISH ERICSSON
AKD 860


Made by Swedish Ericsson

The automatic switchboard AKD 860 is a modern code switch PAX. It is designed for private telephone installations.

In order to cover a wide range of applications and sizes of installations efficiently and economically the PAX comes in units, each for 50 extension lines. The units can be used as individual 50-line exchanges, or combined to form a larger exchange with a maximum of 5 units, thus providing an ultimate capacity of 250 extension lines.

Each 50-line unit permits 5 simultaneous calls within its own 50-unit or to any of the other units. Fully equipped, the exchange can handle 25 simultaneous calls.

This flexible exchange design is also utilised for expansion of the exchange after initial installation. Thus AKD 860 is very suitable for expanding companies that require an exchange which can grow with their needs.

AKD 860 has been designed to meet modern requirements for rapid and efficient operation in combination with reliable service and a minimum of maintenance.

Efficiency and reliability are what have made the crossbar switch famous. The new “code switch” used in this exchange has similar properties, but larger capacity and smaller dimensions.

In addition to satisfying all technical requirements, the code switch has made it possible to house the exchange in cabinets of convenient dimensions suitable for different types of premises.

The cabinets can be mounted against a wall as each rack can be swung out when required. The cabinet can be equipped with lockable doors at the front and a lockable cover at the rear. As the exchange operates silently, it can be mounted wherever convenient, even in an office room.

Ordinary automatic instruments for 48 V current feed with conventional dial can be used. 

By adding auxiliary registers in the exchange, even telephone instruments with galvanic push button dial can be used. In this case both instruments with ordinary dial and the push button dial can be combined in the same exchange.

The extension numbers are:

For 50 line exchanges      10 - 59 or 110 - 159

For 100 line exchanges    100 - 199 (or 00, 01 - 99)

For 150 line exchanges    100 - 199 and 210 - 259

For 200 line exchanges    100 - 299

For 250 line exchanges    100 - 299 and 310 - 359

Certain frequently called extensions (or tie-line routes) can be called by dialling the following single digits: 6, 7, 8, 9 and 0. This does not apply for a 100 line exchange when using two digit numbers as indicated in the table above.

Priority can be given to an unlimited number of extensions merely by strapping in the exchange.

The priority feature enables the extension user who has dialled an engaged extension to cut in on the conversation by dialling “1” after having received busy tone. A warning tone will be emitted automatically to the conversing parties indicating that a third party is on the line. If the called party replaces the handset, a direct connection will be automatically established without the priority extension having to redial.

The Transmission Bridges have split current feed. First party release frees an extension immediately after replacing the handset whether the other party has replaced or not.

Optional facilities which require additional equipment in the exchange are available.

  • Push button dialling.
  • PBX hunting.
  • Tie-lines to other exchanges.
  • Voice paging.
  • Triangular calls (only applicable to extensions with conventional dial).

 

MECHANICAL DESIGN

Cabinets
Each 50 line unit is housed in one cabinet with the following dimensions:

Height 1470 mm (4' 10”)

Width 1025 mm (3' 4”)

Depth 250 mm (10”)

The cabinets come ready wired for the ultimate capacity, and the various types of switching units are connected by means of plug and jack. The interconnection of the cabinets is also based on the plug and jack principle. This has the advantage that assembly can be effected very quickly. Installation and testing thus become extremely simple. Further more, the plug and jack arrangement means that the system can be easily modified and extended without interrupting service.

Each switching unit or relay set in the exchange has an individual dust cover.

If the exchange is installed in an office or room which is used for other purposes than exchange room, the exchange can be equipped with lockable doors. Each unit will than have an appearance of a metal office cabinet. The doors will also give an extra dust protection.

The units (cabinets) can be mounted against a wall as they can be swung out when required. Thereby considerable space will be saved.

The swinging mechanism is simple. It works on a trolley wheel which is actuated by a lever. The mechanism is released by pulling a ring at the front of the cabinet. The cabinet pivots on a steel ball when the chain has been pulled out.

MDF with terminals on the line side for 70 pairs is located behind a cover at the left side of each cabinet. If required further terminal blocks, each for 10 pairs, can easily be added.

The cabinets, relay covers etc. are anti-rust treated, aluminium hammer finished, and stand up well to tropical climates.

The Code Switch
The AKD 860 is a register-controlled system. The selecting stage is con­sist of code switches, which are controlled according to the by-path principle.

The principle for selection of the multiple position in the vertical is based on a mechanical coding method. This is provided by six metal bands (code bands) extending the entire length of the switch and placed just underneath the bank multiple. These code bands are movable length wise independently of each other and are provided with notches forming a system. The coding is achieved through the notches and the relative positioning of the code bands.

The code bands are moved by means of associated code magnets, and the code is transferred to the multiple by individual rocker arms.

Each of the vertical magnets has 17 multiple positions each with 12 levels. By including selection of “floor level”, these terminals can be utilised either for one 12-pole, two 6-pole, three 4-pole or four 3-pole connections. In this way 1, 2, 3, or 4 of the 17 multiple positions are used for selecting “floor level”. The remaining positions are utilised for individual positions as outlets.

In AKD 860, the code switches are all of the same type and have been arranged for 4 “floor levels”, giving 52 outlets of 3 poles.

Due to the design of a new type of contacts as well as a new method for multiple wiring between the verticals, it has become possible to radically reduce the dimensions of the multiple field. The movable contact is a wire spring, the end of which is provided with a cylindrical sleeve of contact material. The stable contact consists of a wire fixed in a plastic support. At each multiple position this wire is formed into V-shaped contacts. This arrangement results in the contacts having twin contact function, despite the fact that each contact consists of one spring. As a result of the operated contact being locked and unable to move in the yoke, a very safe contact function is obtained, unaffected by jolts and vibrations. The move­ment is such that a good self-cleaning action is achieved, which makes the contacts insensitive to dust.

The code switch has ten verticals which are controlled by the same code band and have common multiple. Otherwise each vertical is used as an individual 50 line switch.

The code switches are mounted in a relay unit frame which is inserted in the exchange frame and connected by plug and jack. The multiple connections have special jacks connected straight on to the contact wire-springs from the rear of the switch.

Relays
The relays used in AKD 860 are the well known L M Ericssons telephone relay type RAF and the smaller type “three-in-one relay”.

This latter relay occupies the same space as a normal telephone relay but functions as three individual relays.

Taken from Swedish Ericsson documentation

 
 
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Last revised: September 21, 2010

FM