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
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|
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.
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.
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.
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.
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.
This is for termination of the table version and comprises a two-piece copolymer moulding that can be secured to any flat surface.
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.
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.|
|Instrument Style||Code No.||Description||Keyset format||Type of signalling||BPO Type|
|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|
|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|
Cover, Escutcheon, Handset and Terminal Block
ABS high-impact plastic.
Standard: black, ivory and two-tone grey.
Special orders: red, blue, yellow and two-tone green.
PVC insulated copper-tinsel conductors in a PVC sheath.
Handset cord: coiled, extensible from 10 in (254 mm) to 6 ft (1 82gmm).
Desk cord. 6 ft (1 829mm) standard. Other lengths available.
Microswitch BPO type 20A.
'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.
Black, permanent, and inset on white background to most specifications.
Receiver: BPO type 4T (rocking-armature type).
Transmitter: BPO type 16 (carbon-granule type).
Transmission and reception zero-line sensitivity attenuated by 5dB.
Attenuation decreases with line length to 0db at 400 ohms.
Unicoil type. N9268
Impedance at 25Hz: 3kohms.
Impedance at 1 kHz. 10kohms.
Ringing frequency: 15-30Hz.
Double gong: harmonising tones.
Introduced around 1970.
Click here for a blueprint (290k)
PUBLICATION No.7621, 10/75
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