Patent GB-667067-A (GB)
Title: Improvements in or relating to dials for coin collecting automatic telephones
IPC: H04M17/02
Filed: 1948-11-25
Abstract: 667,067. Coin-box substation apparatus. HALL TELEPHONE ACCESSORIES, Ltd., BUTLER, H. E. J., and YOUNG, A. Dec. 23, 1949 [Nov. 25, 1948; Dec. 13, 1948], Nos. 30628/48 and 32199/48. Class 40 (iv). In a coin collecting telephone instrument for operation from automatic exchanges, the speech transmitter is in general disabled on dialling until coins are inserted, and the dial has two auxiliary contact sets governing two relays, one of which operates to prevent disabling of the speech transmitter when the dial is moved off normal to a predetermined free digit, and to allow free call impulsing during the return to normal, while the second relay operates later than the first on dialling any digit, to prevent restoring of the speech transmitter on non- free digits except by the insertion of coins. A pawl and ratchet mechanism in the dial assembly disables the impulsing contacts if the proper return of the dial from a free call digit is manually interfered with. Fig. 1 shows a dial in which a finger-plate (not shown) is rotatable to a desired digit to wind a spring which on release returns the plate and shaft 2 to normal against a geared governor to generate the appropriate train of line impulses. The shaft carries a ratchet wheel 3; a loose bell-crank lever 4 connected by a pin 14 to a V-lever 11 pivoted at 33 and carrying in turn a pivoted spring-loaded lever 13, adapted to engage the ratchet wheel, having a pin 13A normally holding contacts 24 closed; a freely rotatable cam 5 retaining a pivoted L-shaped arm 20 in the position shown during normal dialling also to hold contacts 24 closed; an operating finger 6 supporting the arm 16 to hold contacts 19 closed when the dial is at rest; an impulse wheel 9 operating contacts 27 through lever 31 and boss 28; and an impulse masking disc 7, frictionally coupled to rotate with the shaft until the finger 7A abuts on the stop 34, which carries a finger 8 co-acting with the finger 6 to prevent opening of the contacts 19 while the dial is rotated off normal. A V-depression in the lever 31 is engageable by lever 4 to interlock with a pin 15 and prevent closure of the impulse springs 27. Lever 11 has teeth 22, 23 interacting with the rightangled portion of lever 20. The usual off normal contacts 25 are closed by a boss 26 integral with finger 6. Holes 29, 30 are positioned in cam 5 to represent digits 0, 9, 8, 7, &c. and pins may be inserted to preselect a free call digit. On off normal rotation of the dial, the boss 26 engages the selection pin and rotates cam 5 to release arm 20 so that contacts 24 are opened before contacts 19. Arm 20 remains unsupported until the dial returns to normal, and pin 13A is also unsupported so that lever 13 is spring urged to engage the ratchet wheel 3, which does not restrain the impulsing movement of the dial. Manual interference intended to produce false impulsing deflects the pivot of lever 13 so that levers 11 and 4 are displaced, the latter interlocking lever 31 and pin 15 to arrest the impulsing contacts 27. To ensure continuity of action and free dialling the end of the arm 20 is retained by a tooth 23 on lever 11. The dial is connected in the circuit of a telephone instrument (Fig. 5) wherein contacts 118, 119, 120 and 121 respectively correspond to contacts 27, 25, 24 and 19 in Fig. 1. On originating a payment call the hand-set is lifted to close contacts 110 111 and 108, 109 and the first digit is dialled, closing the off normal contacts 119 to short circuit the apparatus during dialling. In the dial, finger 6 releases arm 16, which remains supported by finger 8 until the dial is released to return to normal, when arm 16 is freed, contacts 19 (121) are opened until finger 6 returns on the dial reaching its stop position, and contacts 27 (118) are impulsed by wheel 9 to generate the required digital sequence. The opening of contacts 19 (121) operates the slow release relay B, which closes contacts 122, 123 and opens contacts 123A, thus short-circuiting relay A and the speech-transmitter 114, while interrupting the short circuit through the re-closed contacts 19 (121) at contacts 123A. When the called subscriber answers, the appropriate fee is inserted in the coin box (Fig. 4), closes contacts 128, 129, and opens contacts 129, 130 to substitute a coin box transmitter for the speech transmitter so that coin signals are sent to the exchange. The coins pass down a shoot to the arm 135, which opens contacts 116 (Fig. 5) to free the speech transmitter 114 from the short-circuit over contacts 123. Restoration of the hand-set cashes in the coins through lever 138 and opens contacts 110, 111 and 108, 109 to de-energize the instrument and release relay B. When a free digit (e.g. 0 or 9) is dialled, cam 5 in the dial opens contacts 24 (120) before contacts 19 (121), so that relay A operates to close contacts 124 and short-circuit relay B to prevent short-circuiting of the speech transmitter. On dialling a second digit other than 0 or 9, relay B operates as before to shortcircuit the transmitter, and manual interference during free digit dialling is prevented as described above. In a modification, Fig. 6 (not shown), suitable only for systems in which pay numbers do not commence with free digits (e.g. 0 or 9) relays A and B both latch in mechanically on operation until the hand-set is replaced, operation of relay B short-circuiting both relays A and B.