HOUSE EXCHANGE SYSTEMS


House Exchange Systems consist of telephones that can be used for exchange calls or to make internal calls between extensions, without having to connect to an exchange line.

HES 1 & 2
These are based on 300 type telephones with a table mounted 'Unit Transfer Intercom' control unit.  These systems were finally declared obsolete in 1980 although small quantities still existed into the mid eighties.  HES 1&2 were powered by local batteries (with mains operated rectifier) or by a power lead from the local exchange.

HES 3 & 4
HES 3 & 4 are based on 700 type telephones with mains powered, wall mounted relay unit(s) and marketed as 'Keymaster' 1+5 or 2+10 systems, they were declared obsolete in April 1986 but still existed in quantity (particularly HES 4).

All HES systems are hard-wired using multi-cored cable.
These systems were rented, installed and maintained by BT and were approved as `Grandfathered equipment'.


Click on the picture of your choice for more information

hes1a.jpg (37668 bytes) hes2a.jpg (39929 bytes)
HES No. 1 HES No.2
     
hes3z.jpg (14518 bytes) hes4w.jpg (18215 bytes)
HES No. 3 HES No. 4

Click here for HES Prototypes and Pre-Production models

HES 3 and HES 4
The GPO/BT range of House Exchange Systems (HES) is a range of small switching systems comprising telephone instruments with press buttons for accessing exchange lines and extensions.  The telephones are linked together and to the central equipment by multi-wire cabling.

All HES systems were Grandfathered i.e. did not need approval as they existed already.  Facilities include access to exchange line/exchange line barring, intercom with other extensions, conference, hold & transfer and night service.  HES telephones (with press button access to lines and extensions) are referred to as 'Multiple Extensions', 'Non-Multiple' extensions using standard telephones (on e.g. external extensions) and 'Private Circuits' were also provided by use of additional relay units.

There are four systems in the range:-

HES 1, 1 Line and up to 5 'multiple' extensions
HES 2, 2 Lines and up to 10 'multiple' extensions
HES 3, 1 Line and up to 5 'multiple' extensions
HES 4, 2 Lines and up to 10 'multiple' extensions

All the above may be modified to add one more extension.

A limited number of 'Multiple' extensions may be replaced by 'non-multiple' (external) extensions or 'Private Circuits'.


DOCUMENTATION
Diagrams:-
HES 1, Q100 series (Q100 is the Index sheet)
HES 2, Q200 series (Q200 is the Index sheet)
HES 3, Q400 series (Q400 is the Index sheet)
HES 4, Q500 series (Q500 is the Index sheet)
HES 1 & 2 typical layout with multiple extensions only, SA9105
HES 1 & 2 typical layout with multiple and non-multiple extensions, SA9106
HES 3 typical layout with multiple extensions only, SA9174
HES 3 typical layout with multiple and non-multiple extensions, SA9175
HES 4 typical layout with multiple extensions only, SA9209

Engineering Instructions
HES 1 & 2 Telephones, Stations Q1001 Facilities
HES 1 & 2 Telephones, Stations Q1002 Description of Equipment
HES 1 & 2 Telephones, Stations Q1003 Operating procedures
HES 1 & 2 Telephones, Stations Q3001 Installation
HES 1 & 2 Telephones, Stations Q3902 Instructions to subscribers
HES 1 & 2 Telephones, Stations Q4001 Circuit Description
HES 1 & 2 Telephones, Stations Q5001 System Maintenance
HES 3 Telephones, Stations Q1011 Facilities
HES 3 Telephones, Stations Q3011 Installation
HES 3 Telephones, Stations Q4011 Circuit Description
HES 3 Telephones, Stations Q5011 Maintenance of Telephones
HES 3 & 4 Telephones, Stations Q1016 Description of Equipment
HES 4 Telephones, Stations Q1015 Facilities
HES 4 Telephones, Stations Q3015 Installation
HES 4 Telephones, Stations Q4015 Circuit Description
HES 4 Telephones, Stations Q5012 Maintenance of telephones

Telecom Instructions (TI's):-
HES 1 - 4, B4 D0001 HES general
HES 1 - 4 B5 D0009 Sales charges
HES 1 - 4, D7 C2160 Rental charges
HES 1 & 2, B4 D0002 Facilities
HES 1 & 2, C3 C3001 Facilities
HES 1 & 2, C3 C3010 Transmission Standards
HES 1 & 2, C3 C3020 Description
HES 1 & 2, C3 C3021 Operating instructions
HES 1 & 2, E5 D7014 Circuit operation
HES 1 & 2, E5 D7015 Maintenance
HES 3 B4 D0003 Facilities and Apparatus
HES 3 C3 C3030 Facilities
HES 3 C3 C3034 Installation
HES 3 E5 D7034 Maintenance, circuit operation
HES 3 E5 D7035 Maintenance of Telephone No. 3/1F
HES 3 & 4 C3 C3032 Description of Equipment
HES 4 B4 D0004 Facilities and Apparatus
HES 4 C3 C3031 Facilities
HES 4 C3 C3035 Circuit Operation
HES 4 C3 C3036 Installation
HES 4 E5 D7044 Circuit Operation
HES 4 E5 D7045 Maintenance of Telephone No. 4/1F

MAINTENANCE
Maintenance on these systems includes instrument change out, contact cleaning/adjustment and clearing cabling faults.

Maintenance of HES 3 & 4 systems is covered in TI's E5 D7035 and D7045 and includes change out of faulty telephone parts as available or replacement of complete instrument, additionally the springs and contacts of press button units may be adjusted and cleaned on site using standard relay adjustment techniques.

All Identified HES customers should have been contacted by sales groups, in the early nineties, about the future of their systems, any HES encountered on maintenance visits where the customer is not aware of the planned withdrawal (especially HES 1 or 2) should have been referred to sales in case they have not been contacted.

Where a HES was found to be un-maintainable or encountered after the withdrawal date it would have been referred to sales and not automatically replaced by a similar system.

ROUTINE MAINTENANCE
Only on systems powered by batteries, in which case normal battery maintenance should have taken place.

HES 3 & 4 were BT portfolio products and were supported accordingly throughout the remaining product life.  All customers received a letter in January 1992 giving 12 Months notice of BT's Termination of Maintenance and rental on the HES systems.  This was implemented because there was a national shortage of suitable spares and no maintenance would be provided after January 1993.

PARTS
Description						BT Item Code
Telephone Intercom 3/1F Grey (HES 3)                  	41 0274
Telephone Intercom 4/1F Grey (HES 4)                  	41 0277
Transmitter Inset 16                                  	44 3750
Microphone Inset 21                                   	87 7034
Buzzer 33A                                            	37 0093
Lamp 41C                                              	43 1953
Lamp 41E                                              	43 1959
Cord Instrument 20/09 AD Grey, 5000 mm                	51 2038
Cord Instrument 25/06 AD Grey, 3000 mm                	51 2022

Where new parts are not available, re-usable recovered items would have been used as necessary.  Lamps No. 26 H&J (MES type, 7.2 Volt, 0.063 ma) were no longer available, so the nearest commercial equivalents would have been purchased locally and selected to not to overheat or burn out.

BT REPAIR ARRANGEMENTS
By the early nineties repair of HES had ceased at BT factory Cwmcarn.  A limited repair and wipe up facility was offered by GLS Repair for HES 4 terminals.

ADDITIONAL INFORMATION
HES 4 lamps - the lamps are fed via the Regulator No. 4A in the Relay Unit Q516 which limits lamp current to 105 (+/-12) milli Amps.  The regulator can be damaged by lightning or if the 50v DC power supply is reversed on installation.  The lamp current should be checked and if necessary, the regulator replaced at sites where lamps regularly burn out due to a faulty regulator.

Buzzers - HES telephones were originally fitted with (mechanical) Buzzers No. 2B-3, which could wear out, but they may be replaced by (electronic) buzzers 33A.

Taken from BT documentation

 
 
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Last revised: March 19, 2023

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