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Telephone Efficiency Committee
Report on Local Battery Areas
May 1931
Terms of Reference
"To investigate the conditions resulting from the perpetuation of the various alternative
and obsolescent types of subscribers telephones at present in use from a
transmission maintenance and installation standpoint and subsequently to
consider the financial effect of gradually introducing, under annual rental the latest
types of subscribers apparatus for the various types of
exchanges and to report to the "Engineer-in-Chief."
Since the introduction of the new type transmitter unit (Inset No. 10) used in the new
microtelephone (Telephone No. 162) research investigation and circuit
development have been in progress in order to ascertain the effect as regards
Transmission, Maintenance and cost of utilising this type of transmitter for all types
of telephone.
The investigations so far carried out indicate that seriously defective transmission
obtains in the case of local battery instruments fitted with the old pattern micro-telephone. These conditions call for
immediate action and in consequence, this report is an interim one dealing with that aspect of the
case.
Figure 1 shows the old pattern Microtelephone (Telephone No.
28)
Figure 2 shows the new pattern Microtelephone as used in Telephone No. 162.
Figures 3 and 4 show the standard Local Battery instruments of table and wall, type fitted with
fixed transmitters.
Figures 5 and 6 show table sets fitted with Telephone No. 28.
Figures 7 and 8 show wall sets fitted with Telephone No. 28.
Figure 9 shows the instrument given in Figure 5 with a modified cradle fitted with the now Microtelephone as in
Telephone No.162.
Figure 10 shows the instrument given in Figure 7 with a modified cradle fitted with the
new
Microtelephone as in
Telephone No. 162.
Taking the transmission efficiency of the new microtelephone (Fig.2) fitted to
local battery instruments as a base; (a) the Telephone No. 28 fitted to instruments as
shown in Figs. 5, 6, 7 & 8 is about 7 decibels worse for sending efficiency
whilst (b) the table end wall telephones (Figs 3 and 4) fitted with Transmitter Inset
No. 3 are approximately equal for sending efficiency.
The reception efficiency of the new microtelephone is slightly better than either that of (a) or (b).
The articulation of the new microtelephone is in general superior to the
articulation of either (a) or (b) to the extent of from 10% to 25%.
Quite apart from the question of the efficiency of the transmitter, the
question of stability is important. Considerable trouble has been
experienced in the past with both the low efficiency and instability of
Telephone No. 28. The new microtelephone is of far superior mechanical construction to the old pattern of microtelephone, and so far no appreciable change in efficiency of the transmitters or receivers of the new microtelephone has been found in
use.
MAINTENANCE
The day to day maintenance cost for instruments fitted with Telephones No.
28 is much higher than for other types of telephones. It is estimated that this represents an increased cost of £20,000 per
annum. In addition approximately £7,000 per annum for battery power will be saved if Telephones
No. 28 are replaced by the new Microtelephone. The indications are that the maintenance costs for Telephones
No. 162 will be even less than for other types of telephones.
The number of individual subscribers' complaints relating to detective
transmission received by this office approaches 200 per annum and in 60% of these cases the trouble is attributable to the use of instruments fitted with the Telephone No. 28. It will be recognised that the complaints which reach this Office are, in the main, serious
cases and that many complaints are received and dealt with in the Districts without reference to this office.
Tests of an involved nature have to be carried out from a complainant’s telephone through a chain of connections and special staffing by Engineering Officers at points en route is necessitated. This is a costly operation as it makes large demands upon the time of higher grades of the engineering force in arranging the tests and
summarising the results submitted by the officers actually carrying out the
tests. As has already been stated 60% of cases of complaints referred to this office are attributable to the use of the Telephone
No. 28 and it follows that the wastage of force in respect of the local operations is serious and impossible to assess with
exactitude, but it is estimated that this is at least £20,000 per annum.
In addition to individual oases, serious complaints affecting whole areas are being received, e.g.,
Glasgow-Edinburgh (Registered Papers 3987/30 refer) which on close investigation by officers sent from this office, indicated that serious transmission difficulties existed in
communication from local battery areas. The cause was definitely proved to be due in the main to the extensive use of Telephones
No. 28.
Other areas similarly affected end specially reported are Anglesey,
Lancashire, Cumberland, Westmoreland and Yorkshire, and there is reason to believe that the conditions are general for similar areas throughout the country.
The correspondence relating to the subscribers’ complaints which has passed through this Office indicates that the use, of an inefficient
telephone acts as a deterrent in the use of the trunk service. Subscribers have definitely stated in
correspondence that they have abandoned attempts to use the trunk service because of
unsatisfactory transmission.
In accordance with standard instructions, instruments with fixed transmitters have been offered and pressed for in all oases but many subscribers insist on retaining the old pattern
Microtelephone, because of its general convenience of use.
There are approximately, 200,000 Telephones No. 28 in service at the present time or about one tenth of the total telephones in the country. Not only are subscribers’ stations, which are fitted with Telephones
No. 28 affected, but also their correspondents who may have
efficient telephones.
It should be realised that a great majority of these Telephones No. 28 were acquired when the National Telephone
Company's system was transferred to the Department and have either remained in situ since first installed or have been
received from stock.
COST
The Committee have considered the following alternatives, any one of which would
effect the desired transmission improvement:-
- Convert existing instruments fitted with Telephones No. 28, Figures 5 and 7, by fitting the new microtelephone as in Figures 9 and 10.
- Replace existing instruments fitted with Telephones No. 28 by the Complete
new microtelephone instrument. (Telephone No.162).
- Replace existing instruments fitted with Telephones No. 28 Figures 5, 6, 7 and 8, by standard table or wall telephone (Figures 3
and 4).
The procedure of changing the old type micro-telephones for telephones with fixed transmitters is rigidly enforced in the case of
local battery and auto exchange conversions.
As regards alternative (1) it has not been found practicable to modify the types of instruments
shown in Figures 6 and 8 to take the new Microtelephone.
The stock of instruments which are suitable for modification is approximately 12,000 and as there are 200,000 instruments fitted with
Telephones No.28 in service the conversion could not be carried out in a reasonable time. Moreover, there are obvious objections to
making modifications to instruments of an obsolete pattern.
As regards alternative (2) the Department cannot consistently make the change without charging the extra rental proper to the new
Microtelephone instrument (Telephone No. 162).
Alternative (3) offers the least difficulty in execution, as borne out by the experience in connection with exchange system conversions.
There is also a marked advantage as regards the costs of carrying out the
scheme under alternative (3). The total net cost of alternative (1) or (2) is approximately £300,000 with an offset maintenance
saving of £47,000 a year on completion. (The costs been worked out separately
and it is a coincidence that the costs alike for these alternatives).
The total net cost for alternative (3) will be £190,000 with an offset
maintenance saving of £40,000 a year on completion of the scheme.
In the costs for each alternative scheme allowance has been made for
scrapping the recovered instruments fitted with Telephone No. 28 and also for instruments
which will be replaced in normal course during the next few years in connection with exchange
conversions to common battery working.
CONCLUSIONS
The Committee have reached the following conclusions:-
(1) That transmission efficiency is severely handicapped by the use of Telephones
No. 28 and that these instruments should be withdrawn from service.
(2) That Subscribers should be given the option of one of the following alternatives:-
(a) Replace instruments incorporating Telephones No. 28 by the standard pattern
telephone or wall telephone (Figures 3 and 4).
(b) Replace instruments incorporating Telephones No. 28 by the new pattern Telephone No.162 for
C.B.S. or Magneto working where the subscriber agrees to pay the extra rental.
(3) That the change should be made over a period not exceeding three years.
(4) That the issue of instruments fitted with Telephones No. 28 shall cease and
recoveries be scrapped.
(5) That the cost of the proposals (neglecting the possible effect of (2) (b)
will be £190,000 with a saving on maintenance of £40,000 a year on completion of the scheme.
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