Improvements in or relating to arrangements for metering telephone calls

876,538. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO. Ltd. Feb. 12, 1958 [March 12, 1957], No. 8052/57. Class 40 (4). A digit indicative of the duration between metering pulses appropriate to the call is entered in a register on a magnetic drum. The digit is translated into a larger number which is entered in another part of the register and is then reduced by one at each rotation of the drum. When the number is exhausted a metering pulse is sent to line and the cycle repeats. Two embodiments are described. First embodiment, Figs. 2 and 3. Registers on the drum, of the type described in Specification 717,687, are allotted to trunk relay sets as described in Specification 831,188. The register allotted to a call detects a train of impulses PIA from the common translator. This train represents the meter digit and by repeated operation of electronic relay MAN is entered in block TYI of the register. When the called subscriber answers MAA is set and remains set if the apparatus is functioning correctly. MBA is then set during the same scan to return a metering impulse POM to the calling subscriber's meter over gate 12. MBA enables the meter digit to block TYI to set up electronic relays MCA-MFA according to the binary code. The outputs of these relays are translated (Fig. 4, not shown) to enter a corresponding number in the 11 elements of timing blocks TY2, TY3. At the end of the scan MBAMFA are restored. Also when the called subscriber answers electronic relay MGA is set whereby gates 20, 21 reduce by one at each scan the number entered in timing blocks TY2, TY3. When this number is reduced to zero MBA is again set to return another metering pulse and the cycle begins again. At the end of the call MHA is set and the register is cleared. Second embodiment, Figs. 5, 6. The apparatus functions in the manner described above except that translation of the meter code digit is effected by reference to five sections on three library tracks on the drum. The meter code digit is read simultaneously with all possible code digits permanently recorded on the library sections and the translation digits on the library sections are read at the same time as the corresponding elements of the timing blocks TY2. TY3 of the meter register are being scanned. Output from each of the library reading heads is controlled by an associated relay MG1-MG15. When the called subscriber answers, MAA, MCA set MBA, Fig. 6, MBA sets all the library gating relays MG1-MG15. The c