Patent GB-1061001-A (GB)
Title: Improvements in or relating to telephone answering machines
Inventor: PAL GEORGE
IPC: H04M1/652
Filed: 1963-09-27
Abstract: 1,061,001. Telephone answering machines. ROBOPHONE Ltd. Sept. 23, 1964 [Sept. 27, 1963], No. 38241/63. Heading H4K. A telephone answering machine of Specification 1,054,038 is modified to respond to an interrogating code signal consisting of a number of groups of pulses, the machine being provided with a pulse counter for counting the number of pulses in each group and responding to the correct number of pulses in the groups by playing the previously recorded messages back over the telephone line. The main circuit of the machine. Fig. 3 (not shown), and the machine itself, is identical with the machine described in Specification 1,054,038 and therefore only the interrogation code receiver, of which two embodiments are shown, will be described. In one embodiment the interrogation code pulses are produced by speaking mono-syllabic words, or tapping the microphone, e.g. with a pencil. In the other embodiment the pulses are produced using the normal dialling mechanism. Figs. 4A to 4F show one embodiment, for the recognition of, e.g. spoken monosyllables in which, after the answering machine has made its announcement as described in the parent application the incoming signals are applied to the signal amplifier, rectifier, and pulse shaper, formed by transistors Q18 to Q23 to form, from the groups of monosyllabic words, groups of pulses forming the interrogation code. These pulses are applied via lead 124 to a twostage binary counter formed by transistors Q10, Q11, Q12 and Q13, and to a gating circuit formed by transistors Q24 to Q29. Each group of pulses causes the counter to assume a state corresponding to the number of pulses in the group and, at the same time, the pulses, applied to transistor Q24 keep the monostable multivibrator Q25, Q26 in its tripped state until a gap of greater than 1À5 secs, between pulses, i.e. between groups, allows the monostable trigger to relapse and operate the Schmitt trigger Q27, Q28. The pulse from the Schmitt trigger is applied via transistors Q29, Q60 and Q61 to momentarily operate relay L, which via contact L1, Fig. 4D, enables the " AND " gates Q30, Q31, Q32 and Q70, and via contact L2 enables the oscillator circuit Q42, Q43,Q44 to transmit a burst of 1100 c/s. tone to the line to indicate the reception of a pulse group. The inputs to the " AND " gates are derived from the pulse counter via switches 140 to 143 and from the gate selector binary counter formed by transistors Q14 to Q17. The gate selector counter enables AND gates 1, 2, 3 and 4, in turn according to its state of count and the enabled AND gate passes a signal if the setting of the pulse counter Q10 to Q13 is that required for that particular gate as determined by the adjustment of switches 140 to 143, i.e. the interrogation code has been correctly transmitted. If the correct code has been received, the operation of the AND gates triggers the monostable multivibrator Q35, Q36 to its unstable state, in which it stays for 70 milliseconds, at the end of which time the gate selector counter is stepped on by the trailing edge of the 70 millisecond pulse. In addition, the 70 millisecond pulse is applied to cut off transistor Q37 which disables transistor Q38 in the wrong code reset circuit. Had the right number of code pulses not been received, i.e. the pulse counter not reached, or'exceeded, the count selected by the appropriate one of switches 140 to 143, transistor Q37 would have been conducting and allowed any signal appearing on the base of transistor Q38 to be applied to reset the gate selector counter to its original state. The Schmitt trigger Q27, Q28 which operates after a gap of 1À5 seconds in the received pulses also triggers via transistor Q29 and diode 420 a monostable trigger having a 50 millisecond unstable state, the output pulse of which is utilized to reset the pulse counter Q10 to Q13 and also, unless transistor Q37 has been inhibited by the 70 millisecond trigger, resets the gate selector counter via transistor Q38. When the last group of pulses is received No. 4 gate is operated which operates, via transistor Q70, relay E which over contacts E4 discharges capacitor 250 through the base circuit of transistor Q60 and thus operates, via Q61, the relay L for a period exceeding 1 second. In addition contact E2 operates relay G which starts the machine on its replay cycle after first allowing the 1 second burst of 1100 c/s. to be recorded as a " stop replay " signal on the tape. The machine thus winds back to the start of the recording and plays the recordings back over the telephone line, until it reproduces the 1 second burst of 1100 c/s., which is detected by the tuned amplifier Q45, Q46, Q47 and causes transistor Q48 to short-circuit relay G to put the machine into its standby condition. As in the parent Specification, before the machine is put into the standby condition the tape is rewound to a point before the interrogation signal so that the subsequent recording of further messages erases the interrogation signal. In addition the machine is arranged, should the connection be lost during an interrogation replay, to continue the replay, possibly at a higher speed, until the stop replay signal is reproduced to prevent further messages being recorded over unheard messages. In the alternative embodiment for receiving dialled impulses as the interrogation code signal, the receiver is similar to that described above except that the signal amplifier, rectifier, and pulse shaper is replaced by a monostable trigger with a period of about 90 millisecs. which turns the dialling impulses, degraded by the transmission over the exchange lines, into groups of 90 millisecond pulses, which pulses are fed to a pulse counter having four binary stages allowing counts up to ten. In the described embodiment only two groups of pulses are transmitted therefore only two " AND " gates are provided, giving a choice of 100 code groups, although it is suggested that further AND gates and switching banks may be added to give greater security by providing more interrogation code possibilities.