|Minimaster 1 Installation Manual
PXML No. 84
BTHQ CIRCULAR - S1 B8236
This is to introduce the Minimaster 1 which is one of a family of small switching systems
providing up to six extensions with one exchange line. It is ideally suited to the small
Business and Residential markets, providing basic PABX type facilities without the need
for dedicated terminals, or a switchboard; facilities being accessed via the dial or
1. The Minimaster 1 is a microprocessor controlled small switching system which consists
of a mains powered, wall mounted control unit (similar to the Ambassador ESS 1+3) to
which, up to six basic/premium telephones are individually connected by means of a pair of
2. The use of ordinary telephones as extensions allows a wide choice of styles and colours
to be used, but due to technical difficulties Statesman and Sceptre 100 cannot be used
with this system at present.
3. The system is only available with loop disconnect signalling.
4. Dimensions of the control unit are: 300m x 200mm X 75mm
5. The colour of the control unit is light grey.
6. An adjacent power point, minimum 3 amp rating must be provided by the customer.
The following facilities are available:-
- BOTHWAY, exchange line access
- HOLD, any extension may hold an E/L or intercom call while making an enquiry of another
extension. In the event of an exchange line call being put into Hold and forgotten, the
holding extension will be reminded by a short burst of ringing approximately every 15
- TRANSFER, extensions can transfer E/L or intercom calls to another extension within the
system (including an unattended extension).
- CONFERENCE, between the exchange line and two extensions or between three extensions.
- INTERCOM, by dialling the appropriate extension number.
- DIVERT, extensions may divert internal calls to ring at another extension.
- CALL PRIVACY, exchange line and intercom calls are private from other extensions.
- CALL BARRING There are 4 system options of call barring. Each option provides two
choices of barring. These can apply to all extensions except extension 1 which cannot be
barred at all. Once a barring option has been chosen, it can only be changed by a BT
Barring options are as follows:-
(i) No Barring or full barring
(ii) No Barring or IDD barred
(iii) IDD barred or IDD and STD barred
(iv) IDD barred or full barring
Once a barring option 1-4 has been chosen, one of the two alternatives for each extension
is then programmed by the installer. It is important that customers are made aware of the
(a) IDD and STD call barring applies to dialled calls only, it does not apply to operator
(b) Full barring does not allow 999 calls
(c) STD barring will also prevent the dialling of local calls beginning with 101.
PROGRAMMED RINGING FOR EXCHANGE LINES
Telephones connected to the Minimaster1 ring
sequentially, not together. There is a choice of ringing programmes (5 in all) which will
ring 1, 3 or all 6 telephones. The ringing cycle is repeated until the call is answered or
the caller clears down.
Programme 1 rings extension 1 only
Programme 2 rings extension 2 only
Programme 3 rings extension 22.214.171.124.5.6 (in that order)
Programme 4 rings extension 1.3.5 (in that order)
Programme 5 rings all extensions 1- 6 in sequence
The sequence of ringing is 6 rings at the first extension, 4 rings at the second and third
extensions then 2 rings at each subsequent extension. During the ringing cycle the call
can be answered at any extension that is not ringing by lifting the handset and dialling
8. A full ringing sequence, i.e. all telephones rung, takes approximately 1 minute.
The customer selects the most suitable ringing programme which is programmed on
installation. Because of the exchange line ringing cycle and the mains failure facilities,
the customer should give careful consideration to the extension numbering scheme.
ADDITIONAL PHONE SOCKETS
Additional sockets may be provided on extensions, within the normal limits.
Minimaster 1 will cater for external extensions working within the prescribed transmission
Under mains failure conditions extension 1 becomes a direct exchange line, all other
facilities are lost.
Operating instructions will be included with each control unit.
1. As a first step in the market with this type of product, contracts have been placed
with two contractors for different versions of Minimaster. The first of these is
Minimaster 1 which is currently undergoing trial in the Tunbridge Wells Telephone Area of
BTSE. Marketing will follow in the remainder of BTSE and then be extended to BTL and BTM
by the end of 1982.
The second system, to be marketed as Minimaster 2 will be supplied by another manufacturer
and be available to the remaining 7 regions from the end of 1982 early 1983. The
Minimaster 2 has a capacity of 1 exchange line and 5 extensions, provides similar
facilities to Minimaster 1 and will be the subject of a separate BTHQ Circular.
2. Minimaster systems will not, initially be nationally promoted. However, Regions/Areas
may originate their own local campaigns in order to create awareness.
FIELD OF USE
Minimaster 1 may be used in all situations EXCEPT:
(a) Shared Service
(b) MF PBX's and exchanges
(c) As plan extensions
(d) DC CODE C systems
(e) Statesman and Sceptre telephones are not suitable
The following telephones are suitable as extensions to Minimaster 1 Basic dial/press
button, Ambassador, Astrophon, Candlestick, Contempra, Viscount.
Battery powered telephones i.e. Xpress callmakers and early versions of press button
telephones e.g. Tele 764, must be provided with power unit 53B when used on extensions of
NOTE: When Minimaster 1 is used on PBX extension, the telephones associated with
Minimaster must be fitted with a recall button.
TWO NEW wall-mounted small switching systems are being introduced this year. The
systems - the Minimaster 1 (1 + 6) and Minimaster 2 (1 + 5) - are aimed at small business
customers but the choice of extension telephones will make the systems attractive to
residential customers as well. As a first step into these markets, contracts have been
placed with two manufacturers for the different versions of Minimaster. The systems are
similar in design, comprising a mains-powered central control unit to which extensions are
individually connected. Minimaster 1 is currently being trailed in Tunbridge Wells
telephone area and Minimaster 2 is shortly to undergo trials in Southend area.
Taken from BT Management News - April 1983