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 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 multicored cable.
These systems were rented, installed and maintained by BT and were approved as
Click on the picture of your choice
|HES No. 1
|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 multiwire
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 TIs 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
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.
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.
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
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