Inexpensive device permits measurement and remote interrogation of variables such as voltage, temperature, pressure, or humidity by standard telephone equipment. Remote interrogation of wind direction and velocity, humidity, or water levels on flood-prone river are other possible representative uses for this device

Miller, R. L.

English

NASA Technical Reports Server

March 1973
	
B73-10010 
NASA TECH BRIEF 
Lewis Research Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service. Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington. D.C. 20546. 
REMOTE MEASUREMENTS BY TELEPHONE 
Basic Telephone Measurement Device 
Data Signal (DR) I 
-	 I 
Phone f-.----
Line 
-v 1l s	 Off Hook (OH) 
I	 I JLJ
Ring Indicator (R1)I 
Model 1001B 
Linear 
Analog
	 Gate 
Input 
0
Sequence Counttr 
_j
Figure 1 
An inexpensive device, shown in Figure 1, permits the 
measurement and remote interrogation of variables such 
as voltage, temperature, pressure, or humidity by standard 
telephone equipment. When a caller dials the number to 
which the device is connected, it "answers" the telephone, 
measures the variable to which it is connected, and 
produces a series of zero to ten "beeps" proportional to 
the variable. The device then "hangs up" the telephone 
and awaits the next call. 
This device connects to the telephone line through a 
Model IOOIB Data Coupler manufactured by American 
Telephone and Telegraph Co. The coupler supplies a ring 
indicator (RI) signal when a call is received. It is 
instructed to answer the call by the off hook (OH) signal 
from the device, and is supplied with audio information 
on the data signal (DR) line. 
Sequencing is accomplished by a 2 hertz oscillator and 
a sequence counter. When a RI signal is received, SCR1 
fires and pulls relay R. The relay contacts supply an 01-I
signal to the coupler and remove a reset level from the 
sequence counter, allowing it to count pulses from the 2 
hertz oscillator. During the first three counts, linear gate 
A2
 is open, connecting the input analog signal to the 
analog-to-digital (A-D) converter. A sample and hold 
circuit stores this analog voltage for later conversion. 
When the count reaches 4, at 2 seconds, a logic one level 
from the Or gate causes the conversion of the stored 
voltage to begin. At this time also, linear gate A 2 is turned 
off through the inverter. The A-D converter output goes 
positive for a time period proportional to the stored 
analog voltage. This allows a series of I khz pulse bursts, 
at a 2 hertz rate, to be gated out through A 1 to the 
coupler DR line. This results in a series of "beeps" 
proportional to the measurement. 
k	 4P	 (continued overleaf) 
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Multiple Input Configuration
I OSC. 
I 2 kHz Linear	 I 
Analog	
Gates 
Input 1 
Analog 	 J Convert Input 2 TIA
0	 16 A M 
OSC.FA 
I 
.
8 164 8 1 
- F- 
_ 
4 - 
8 16^ 
:2H az - I
Sequence Counter 
Figure 2
I 
Data Signal (DR) 
The convert level remains in the logic one state until 
the counter reaches 16, at 8 seconds, at which time SCR 
is fired by the sequence counter carry pulse, and SCR 1
 is 
reset. This drops relay R, removing the OH signal to the 
coupler, which "hangs up" the telephone. 
Figure 2 shows how multiple analog inputs can be 
sampled in sequence by adding more stages to the 
sequencing counter. The analog inputs can then be gated 
into the A-D converter and read out in sequence by these 
additional stages. Different tone generators can also be 
used for each input to differentiate the inputs being 
sampled. 
NOTES: 
1. Non-inverting And and Or circuits were used through-
out. 
2. This device was designed to interrogate the status of 
two large time-sharing computer systems. Inputs were 
analog voltages proportional to computer usage. How-
ever, such applications as remote interrogation of 
temperatures or pressures in unattended installations 
can easily be accommodated. Remote interrogation of 
wind direction and velocity, humidity, or water levels 
on a flood-prone river are other possible representative 
uses for this device.
3. No additional documentation is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B73-10010 
PATENT STATUS: 
NASA has decided not to apply for a patent. 
Source: Robert L. Miller
Lewis Research Center
(LEW-1 1704)
0- 
B73-lOOlO	
.	 Category 01,02


Remote measurements by telephone

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