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

HES 3 and HES 4
The 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'.

The Following diagrams cover HES:-

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 extns only, SA 9105
HES 1/2 typical layout with multiple and non-multiple extns, SA 9106
HES 3 typical layout with multiple extns only, SA 9174
HES 3 typical layout with multiple and non-multiple extns, SA 9175
HES 4 typical layout with multiple extns only, SA 9209

The following Telecom Instructions (TI's) may be referred to:-

HES 1 - 4, B4D 0001 HES general
HES 1 & 2, B4D 0002 Facilities
HES 1 & 2, C3C 3001 Facilities
HES 1 & 2, C3C 3010 Transmission Standards
HES 1 & 2, C3C 3020 Description
HES 1 & 2, C3C 3021 Operating instructions
HES 1 & 2, E5D 7014 Circuit operation
HES 1 & 2, E5D 7015 Maintenance
HES 3 B4D 0003 Facilities and Apparatus
HES 3 C3C 3034 Installation
HES 3 E5D 7034 Maintenance, circuit operation
HES 3 E5D 7035 Maintenance of Tele 3/1F
HES 4 B4D 0004 Facilities and Apparatus
HES 4 C3C 3031 Facilities
HES 3 & 4 C3C 3032 Description of Equipment
HES 4 C3C 3035 Circuit Operation
HES 4 C3C 3036 Installation
HES 4 E5D 7044 Circuit Operation
HES 4 E5D 7045 Maintenance of Tele 4/1F

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 D 7035 and 7045 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 unmaintainable or encountered after the withdrawal date it would have been referred to sales and not automatically replaced by a similar system.

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

HES 3 & 4 are portfolio products and will be supported accordingly throughout remaining product life.  All customers will receive a letter in January 1992 giving 12 Months notice of BT's Termination of Maintenance and rental on HES.  This is being implemented because there is a national shortage of suitable spares, no maintenance will be provided after January 1993.

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 should be used as necessary.  Lamps 26 H&J (MES type, 7.2 Volt, 0.063 ma) are no longer available, where nearest commercial equivalents are purchased locally they must be selected not to overheat or burn out.

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.

HES 4 lamps - the lamps are fed via the Regulator 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 2B-3 which can wear out, they may be replaced by (electronic) buzzers 33A.

Taken from BT documentation

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Last revised: February 18, 2021