LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747 (516) 271-0400 FAX (516) 271-0405
TONE ACTIVATED TELEPHONE LINE SWITCH CONTROLLERS
• Circuit activated by Tone with specific Frequency and
• Frequency and Time Duration values are mask
• Small Signal (as low as - 30 DBM) and Digital Level
Tone signals accommodated.
• On-chip active oscillator network and 32,768 Hz
Crystal generates timing.
• Low power consumption.
• +4.0V to +6V operation (VDD - VSS).
• Remote telephone line testing
• Remote meter reading
• Security system dialers.
CONNECTION DIAGRAM - TOP VIEW
STANDARD 16 PIN PLASTIC DIP
TIME BASE 2
VF OUT 3
VI OUT 4
DTEN INPUT 6
16 V DD (+V)
13 DIGITAL TONE
12 AMP IN
11 AMP OUT
The LS7501 - LS7510 are CMOS frequency discriminator
circuits designed to respond to a specific frequency
TONE signal when that frequency is maintained within
+10Hz during a continuous 4.5 second Sample Interval
Time. When a valid TONE occurs the Set Relay Level
output goes high for 20 seconds.
A typical application will use the Set Relay Level output
to temporarily switch the telephone line connection.
Valid Frequencies are mask programmable from 11Hz to
4095 Hz, in 1 Hz steps. Valid Sample Interval Times are
mask-programmable from 0.5 seconds to 8.0 seconds, in
0.5 second steps. Table 1 shows mask programmable
options for the available LS7501 - LS7510 part numbers.
Table 1. MASK PROGRAMMED OPTIONS
Part # Frequency (Hz) Part # Frequency (Hz)
NOTE: All Part Numbers are programmed with a Sample
Interval Time of 4.5 seconds. Referring to the LS75XX
Block Diagram (Figure 2) each Part Number has the Set
Relay Level option on Pin 8. The 32 KHz option is on Pin
2 with one exception. LS7502 has the 8Hz option.
SET RELAY PULSE 7
SET RELAY LEVEL 8
9 V SS (-V)
Referencing Figure 2, an external C is used to generate a
Power-On Reset pulse at Pin 10. When the Frequency Dis-
criminator samples a valid frequency at Pin 13 for an entire
0.5 second sample period, Pin 3 goes high and the Sample
Interval Timer begins timing. If the Pin 13 frequency is not
valid during any subsequent sample period, Pin 3 goes low
and resets the Sample Interval Timer. When Pin 13 fre-
quency is valid for the programmed period of the Sample In-
terval Timer, a high-going pulse occurs at Pin 4. Normally,
Pin 4 externally connects to Pin 6 and the pulse will cause
the Frequency Discriminator to be disabled, enable the Dis-
connect Timer and bring Set Relay Level high at Pin 8.
When the Disconnect Timer times out (20 seconds) a high-
going pulseoccurs at Pin 1. Normally, Pin 1 externally con-
nects to Pin 5 and the pulse will cause the Frequency Dis-
criminator to be enabled, disable the Disconnect Timer and
bring Set Relay Level low at Pin 8. The circuit operating se-
quence begins again.
A digital level Tone signal connects to Pin 13. A small-signal
Tone frequency should be AC coupled to Pin 12 with Pin 11
externally connected to Pin 13. The 32,768 Hz crystal con-
nects between Pin 14 and Pin 15. Pin 10 has an internal