3 Internal
Issue 1, June 1978


The Self Contained (SC) Keysender No. 1 is available for use on Multipled PMBX's.

It is introduced to the customer as an alternative to the conventional rotary dial on PMBX's 1A, 1B and PMBX 4/1A installations.

keyun4_1.jpg (7234 bytes)The SC Keysender No. 1 comprises the Key Unit No. 4/1A (show pictured to the right) and the Sender Unit No. 9B-1.

The Key Unit No. 4/1A is mounted in place of the operators dial. It has a 3-3-3-1 key format integral with a Cancel Key marked "-" and an amber supervisory lamp.

Keyed in numbers will be stored in the sender 9B-1 which is located within the switchboard and has a capacity of 16 digits. The sender will transmit loop disconnect pulses to line (at 10pps) as soon as the first digit has been keyed-in. The amber supervisory lamp will, by remaining alight, indicate that stored digits are being transmitted.

The keysender, utilises the PMBX power supply, and therefore keysenders fitted to PMBX 4/1A installations powered directly from the mains will become inoperative under mains fail conditions. Keysenders on PMBX 1A, 1B, and PMBX 4/1A with standby power will remain operative so long as there is sufficient charge in the floated battery system provided on these types of installations. On PMBX 1A and 1B installations a Voltage Regulator Unit 13A is required. This is necessary because there is no voltage regulator circuit on these installations. It should be noted that a faulty SC Keysender No. 1 cannot be changed by the PBX Operator.

Provision of the SC Keysender No. 1 should be restricted to PMBX 4/1A, PMBX 1A and PMBX 1B installations.

The SC Keysender No. 1 may be provided on installations where two non- multiple PMBX 4/1A are installed provided the Long Cord Kits (Kits 227B) are fitted to each position.

Due to operating reasons it is generally undesirable to mix dial and Keysender No. 1 at one installation, so where keysending facilities are requested it is recommended that the SC Keysender No. 1 is provided at each position.

Sender No. 9B-1

Follow the usual procedure for making a dialled call until dialling tone is received then:-

(i) Operate the Dial/Ring Back Key to the Dial position on PMBX 1As or 1Bs or the Speak/Dial Key to the Dial position on a PMBX 4/1A.

(ii) Key the number you require one digit at a time.

It is not necessary to pause between key operations while a digit is pulsed out. The Amber supervisory lamp glows while these pulses are being sent. Do NOT restore the 'Dial/Ring Back or the Speak/Dial keys to normal until the Amber lamp has gone out.

If a wrong number has been keyed press the Cancel Key (marked -) withdraw the calling cord for at least two seconds and set the call up again.

Specifications S(W) 2206A and 2207A outline the work to be carried out on PMBXs 1A, 1B and multipled PMBX 4/1A switchboards to convert them for operation with the SC Keysender No. 1.

S(W) 2206A applies to PMBX's 1A and 1B. S(W) 2207A applies to PMBX 4/1A.

The following stores are required per switchboard position for the keysender conversion on PMBX 4/1A installations:-

Sender Unit No. 9B-1 - 1
Tape adhesive fixing 1" - As required
(Suitable angle iron 32 mm x 32 mm x 165 mm) - 1
Self-tapping screw, Type A No. 10 panhead 13 mm - 2
Key Unit No. 4/1A 1 Plate, mounting No. 5D - 1
Self-tapping screw, Type A No. 6 panhead 13 mm - 4
Jack No. 83A - 1
Cable, Equipment No. 5762A, lap screened
Fuse No. 44A/0.5 (Blue) - 1
Sleeving No. 7C Green

The following stores are required per switchboard position for the keysender conversion on PMBX 1A and 1B installations-.-

Key Unit No. 4/1A - 1
Wood Screw No. 4 x 13 mm Rd Hd Brass - 4
Sender Unit 9B-1 - 1
Tape Adhesive Fixing 1" As required
Voltage Regulator Unit - 1
Wood Screw No. 4 x 19 mm Rd Hd Brass - 2
Cable Equipment No. 5762A, lap screened - As required
Sleeving No. 7C green - As required
Fuse No. 44A/0.5 (blue)
Jack No. 83A
IENOXI Type cutter 1" (hole saw)
Tape, insulating, adhesive - As required


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Last revised: January 21, 2021