Press button Telephones
DC & MF These BPO approved DC and MF (multi-frequency) press button telephones are
structurally similar to the BPO type 746 telephone but incorporate a press button Keyset
instead of the conventional rotary dial for speed, convenience and reliability in the
setting up of calls.
Both types are available as table and wall-mounted instruments and are suitable for
working into fast switching systems that employ either DC (ITT code C) or MF
(CCITT-recommended 1/4 + 1/4 VF) signalling.
Main Design Features
Modular, robust construction
High-speed signalling
 Precise press button action
Easily visible Keyset characters
Non-adjust Keyset-spring gaps and tensions
Printed-circuit boards with miniature components
Automatic line regulator
Stain-resistant, high-impact moulding
Integral recessed carrying handle
Optional press button for operator recall, shared service etc.
Standard or tropical finish.
Cover and Escutcheon
The cover and escutcheon plate are colour fast ABS copolymer mouldings of high-impact
strength and high-gloss finish.
The cover incorporates a recessed carrying handle, and a dummy button that is easily
replaced by a press button when shared-service or operator-recall facilities are required.
The escutcheon plate is held to the cover by four metal clips that allow limited
lateral movement to ensure correct cover-to-baseplate relationship when the cover is
replaced. Provision is made on the escutcheon for a label under a clear plastic window to
display the subscriber's number and/or supplementary information as required.
 |
 |
| DC version with case removed |
MF version showing the oscillator in the
foreground |
Keyset
The Keyset comprises press buttons, printed-circuit board with associated high-quality
miniature components and buttons laid out to CCITT recommendations.
The digits 1 to 0 are arranged in a 3 - 3 - 3 - 1 pattern and read from left to right. Two
other buttons, generally used for extra facilities and marked ) * and # are situated
either side of the 0 button, forming a 3 - 4 format.
The 'break-through' characteristic of the press buttons eliminates any false contact
operation, and therefore false signals.
The concave-faced white buttons have black, permanent, inset-moulded characters and are
push fitted on to the key stems. Button markings can be provided to most specifications.
DC telephones with a 10 button Keyset format (3 x 3 x 3 + 1 ) are available for orders of
sufficient quantity.
Oscillator (MF only)
 The printed-circuit oscillator board is fitted to the rear verticals of the
cradle switch and powered from the exchange battery.
It comprises high-quality components, ensuring stability of output under the most
adverse conditions of ambient temperature, humidity and exchange-battery voltage.
Handset
The handset is a lightweight, one-piece moulding with screw-fitted mouthpiece and
earpiece. The cord is bayonet clamped and the transmitter and receiver inserts are
connected by screw terminals for good connection.
Cords
The cord conductors for both desk and handset cords are copper-tinsel with PVC insulation
and spade terminals. The outer sheath is of flexible PVC. The handset cord is the coiled
extensible type. Grommets, fitted to both ends of the cords, lock into entry holes of the
terminal block and main instrument and act as strainers.
Baseplate
The baseplate is moulded in toughened polystyrene and rests on four chloroprene non-stain
feet to prevent the instrument from sliding. All interior parts of the instrument, cradle
switch bracket, ringer and gongs, Keyset assembly and printed-wiring board are mounted on
the baseplate.
Printed-wiring Board
A printed wiring board accommodates all speech circuit components except the transducers,
and terminates all incoming and outgoing connections. The cradle micro switch has a low
operating pressure and requires no maintenance. The regulator maintains constant speech
levels irrespective of line lengths. Unregulated instruments can be supplied for
large-quantity orders.
Terminal Block
This is for termination of the table version and comprises a two-piece copolymer moulding
that can be secured to any flat surface.
Simplified Maintenance
The cover is easily removed on the release of a single screw at the base of the telephone.
The cradle switch can be locked by a manually operated latch to allow incoming calls to
be signalled during instrument inspection.
All cord conductors are spade terminated to provide easy connection to the instrument
wiring board and terminal block.
Ringer, bell gongs, Keyset, oscillator board and printed wiring board are readily
accessible and easily replaced.
Robust construction and reliable components ensure trouble-free operation over long
periods.
Colour Range
Standard colours are black, ivory and two-tone grey, but demands for special colours (red,
blue, yellow and two-tone green) can be met for instruments ordered in sufficient
quantity. In two-tone colours, the handset, cords and terminal block are in the darker
tone.
Dimensions and Weights
| Style |
Height ins. |
Width ins. |
Depth ins. |
Weight lbs. |
| Table telephone |
4.5 |
9.3 |
8.9 |
5 |
| Wall telephone |
8.5 |
9.3 |
5.5 |
5 |
Telephone Types
| Instrument Style |
Code No. |
Description |
Keyset format |
Type of signalling |
BPO Type |
| Table |
N2060A |
PB standard |
3x3+1 |
DC |
- |
| Table |
N2060B |
PB standard |
3x4 |
DC |
3A-2 |
| Table, Blue |
N2060B5 |
PB standard |
3x4 |
DC |
SA4252 |
| Table, Grey |
N2060B6 |
PB standard |
3x4 |
DC |
SA4252 |
| Table |
N2063B |
PB two lamps (sim 740) |
|
DC |
|
| Table Yellow |
N2063B4 |
PB two lamps (sim 740) |
|
DC |
2/SA4252 |
| Table |
N2064B |
PB two lamps (sim 740) |
|
|
|
| Table |
N2064B1 - B7 |
B two lamps (sim 740) |
|
|
2/SA4252 |
| Table |
N2067A |
PB one lamp (sim 740) |
3x3+1 |
LD |
|
| Table |
N2069B |
PB 2 lamp (sim 740) |
3x4 |
DC |
|
| Table Yellow |
N2069B4 |
PB 2 lamp (sim 740) |
3x4 |
DC |
4/SA4252 |
| Wall Grey |
N2070B6 |
PB standard |
3x4 |
DC |
3/SA4252 |
| Wall |
N2070B |
PB standard |
3x4 |
DC |
3B-2 |
| Table |
N2080B |
PB standard |
3x4 |
MF |
4A |
| Table |
N2080B6 & B13 |
PB standard |
3x4 |
MF |
SA4258 |
| Table |
N2083B |
PB (sim 740) |
3x4 |
MF |
|
| Wall |
N2090B |
PB two lamps (sim 740) |
3x4 |
MF |
4B |
Abridged specification
Cover, Escutcheon, Handset and Terminal Block
ABS high-impact plastic.
Baseplate
Toughened polystyrene.
Colours
Standard: black, ivory and two-tone grey.
Special orders: red, blue, yellow and two-tone green.
Cords
PVC insulated copper-tinsel conductors in a PVC sheath.
Spade terminations.
Handset cord: coiled, extensible from 10 in (254 mm) to 6 ft (1 82gmm).
Desk cord. 6 ft (1 829mm) standard. Other lengths available.
Cradle switch
Microswitch BPO type 20A.
Keyset
'Break-through' action press button type with non-adjust phosphor-bronze springsets that
are gold-silver plated at the contact area.
Oscillator (MF only)
Single transistor printed-circuit oscillator board providing stable multi-frequency
oscillations for 1/4 + 1/4 VF signalling.
Button Characters
Black, permanent, and inset on white background to most specifications.
Handset Transducers
Receiver: BPO type 4T (rocking-armature type).
Transmitter: BPO type 16 (carbon-granule type).
Regulator
Transmission and reception zero-line sensitivity attenuated by 5dB.
Attenuation decreases with line length to 0db at 400 ohms.
Ringer
Unicoil type: N9268
Resistance: 1kohms
Impedance at 25Hz:.3kohms.
Impedance at 1 kHz: 10kohms.
Ringing frequency: 15-30Hz.
Bell Gongs
Double gong: harmonising tones.
Introduced around 1970.
Click here for a blueprint
PUBLICATION No.7621, 10/75
|
