Second, the ground signal at E13 is applied to or-gate U1- A, which energizes relay K1 through switch U1-B. First, switch Q1 turns on, thereby applying a positive signal to the COR input on the COR Board. When the DTMF De - coder/controller Board applies a ground signal to E13, two things happen. DTMF tones from either the phone line or the receiver are applied to the DTMF De coder/controller Module through E8. C8 is a bypass for low frequency rf which may be present on the telephone line. (The high gain needed in U1-D for the weak phone audio would cause distortion of the receiver audio if allowed to take the same path as the phone audio.) VR1/VR2 is a pair of back-to-back zener diodes to absorb the inductive surge when Q4 is switched off, thus preventing transistor damage. Because U1- D is off during this condition, the amplified audio from Q4 is blocked from the input of U1-C through this second path. Bias for the stage is switched on by Q2 only when the receiver squelch is open.
Receiver audio is applied through potentiometer R1 to line driver Q4, which amplifies the signal and drives the telephone line through isolation transformer T1.
Capacitor C15 works in conjunction with a diode on the TD-2 DTMF De coder/controller Board to provide a fast-attack/slow-release time constant for the mute switch. This prevents tones from being repeated on the transmitter. Q5 acts as a switch to mute the audio at the input of U1-C whenever the DTMF Decoder/Controller Board applies a signal indicating that tones are being received. Thus, receiver audio does not interfere with audio coming from the telephone line. Because of the squelch action in the receiver, audio is present only when a station is heard on the receiver. Some of this audio is applied through R16 and mixer U1-C and E9 to the transmit audio input circuit on the COR board. Audio from the repeater receiver enters at E7. The 220 pf capacitors at various input and output terminals of the board are to bypass vhf/uhf rf energy. C10 prevents switching clicks from occurring when a dc signal is applied through R12 or R13. Therefore, the radio station using the repeater has control over what parts of the incoming telephone conversation goes out over the air: any time the radio operator keys his microphone, the receiver squelch cuts off the telephone audio at U1-D. 65 Moul Rd Hilton NY Phone: and the receiver squelch is closed.
U1- D also acts as a switch: audio passes only when the autopatch is enabled HOW TO CONTACT US Hamtronics, Inc. The repeat phone line level is set by potentiometer R8. Phone line audio is amplified in two successive op-amp stages. When the autopatch is enabled, relay K1 connects the telephone line to isolation transformer T1 through dc blocking capacitor C5. When the opto-coupler senses a ringing voltage on the line, it trips timer U3. When the phone line is "on-hook", any incoming ac ringing voltage is coupled through capa citors C6 and C99 to opto-coupler U2.
When the phone patch relay is activated, the dc current drawn by R6/R7 "seizes" the phone line, and T1 couples audio in and out of the line. Relay K1 completes a path to dc load resistors R6/R7 and to isolation transformer T1 via high voltage capacitor C5. Refer to the schematic diagram and the repeater block diagram during the following discussions. It is registered with the FCC under part 68. The Autopatch Module can be interfaced directly with any touchtone telephone line. The Autopatch Module is used with the DTMF Decoder/Controller Module to provide the following functions: repeater autopatch, reverse autopatch, primary phone line remote control of repeater, phone line monitor of repeater receiver, and secondary remote control through repeater receiver. 1 HAMTRONICS AP-3 AUTOPATCH MODULE: INSTRUCTION MANUAL FUNCTIONAL DESCRIPTION.