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.

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.

The Committee have considered the following alternatives, any one of which would effect the desired transmission improvement:-

  1. Convert existing instruments fitted with Telephones No. 28, Figures 5 and 7, by fitting the new microtelephone as in Figures 9 and 10.
  2. Replace existing instruments fitted with Telephones No. 28 by the Complete new microtelephone instrument. (Telephone No.162).
  3. 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.

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.

Fig. 1 Telephone No. 28 (old pattern microtelephone)
Fig. 2 Telephone No. 164 or 184 (new pattern microtelephone)
Fig. 3 Telephone No. 4 (Standard LB table instrument)
Fig. 4 Telephone No. 11 (Standard LB wall instrument)
Fig. 5 Telephone No. 88 Mk NT. 13
Fig. 6 Telephone No. 16
Fig. 7  Telephone No. 59 (bell below desk)
Fig. 8 Telephone No. 59 (bell above desk)
Fig. 9 Telephone No. 88 Mk NT. 13 with new microtelephone
Fig. 10 Telephone No. 59 (bell below desk) with new microtelephone


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