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AKD 735, Code Switch P.A.B.X. for 30 Extensions A. GUDMARK & B. ROMARE, TELEFONAKTIEBOLAGET L M ERICSSON, STOCKHOLM UDC 621.395.25 LME 8372 This article presents a Code Switch P.A.B.X. designed to cover requirements up to 30 extensions and 7 exchange lines. The new P.A.B.X., AKD 735, is a register-controlled code switch unit working on the bypath principle. LM Ericsson's new 30-line P.A.B.X., AKD 735. is characterized by high traffic capacity, low maintenance expenditure and silent operation. The equipment is accommodated in a grey-enamelled rack which takes up little space and harmonizes well with modern office furnishings (fig. 1). The exchange is based on the code switch (with pressure contacts of precious metal), the small operating movements of which result in a minimum of wear. The exchange therefore has a long life and costs very little in maintenance. The maximum capacity of the exchange is 30 extensions, 7 exchange lines and 4 internal connecting circuits. Fig. 1 Code switch exchange AKD 735 (Right) with doors open AKD 735 has a very high traffic capacity. When fully equipped, up to 15 extensions can be conversing at the same time. AKD 735 can also be furnished with all the traffic facilities required by a modern enterprise. 90
The standard model of AKD 735 incorporates a number of traffic facilities such as enquiry calls, transfer, automatic camp-on, priority, busy lamps, two types of night service connection, etc. With additional equipment various special services can be obtained such as automatic paging, supervision of dialled trunk calls, group calls, etc. The operator's console (fig. 2) is of modern design with a grey plastic cover. Since each extension is represented by its own key on the console, incoming calls can be put through very quickly. The extension telephones are normal telephone sets with earth button. Traffic Facilities Internal calls. The extensions have two-digit numbers and the operator a one-digit number. Four internal conversations can take place simultaneously. External calls. Calls to the public exchange are initiated by a single-digit prefix. Incoming calls are indicated on the operator's console. Connection to the extension is effected by pressing a key. Under night service conditions calls can be answered from one or more extensions. Priority. Any extension can be given priority, which implies that the extension can enter an engaged circuit. A faint busy tone is issued to the conversing parties to indicate that a third party is on the line. Extension categories. The extensions can be divided into four categories, viz.: • Unrestricted extensions with full traffic facilities. • Trunk-restricted extensions with facilities for all kinds of traffic except dialled trunk calls. (Trunk discrimination equipment is required for this purpose.) • Semi-restricted extensions with full internal traffic facilities. These can receive incoming calls from the public exchange, but external calls can only be set up with the assistance of an operator. • Restricted extensions which can be used for internal calls only. All external traffic is barred. The extensions can be allotted individually to any desired category. Enquiry calls. During an external conversation an enquiry call can be made to another extension, to the operator, or via an exchange line to a public exchange subscriber. Transfer. External calls can be automatically transferred any number of times either to an extension or to the operator. Night service. There are two types of night service, viz.: • Individual night service, which implies that incoming calls are automatically put through to predetermined extensions connected to the respective exchange lines. The exchange lines can also be combined into groups. D Common night service, which implies that incoming calls are signalled on one or more separate bells. The call can be answered on any non-restricted extension. Serial calls. An incoming call can be put on a "series circuit" by the operator, which means that it is automatically reconnected to the operator after each completed conversation. In this way the operator can connect the call to a number of extensions in the desired sequence. Parking. The operator can place an incoming call on a parking circuit. In order that a parked call shall not be forgotten, the operator is recalled automatically after about 30 seconds. 91
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