The Company's gross profit increased by $8,019,000 to $19,462,000, or 46.0% of net sales, for the three months ended December 31, 2022 as compared to $11,443,000, or 34.3% of net sales, for the same period a year ago. Gross profit on equipment sales was $6,247,000, or 22.8% of net equipment sales, for the three months ended December 31, 2022 and $1,809,000, or 8.1% of net equipment sales, for the same period a year ago. Gross profit on service revenues was $13,215,000, or 88.8% of net service revenues, for the three months ended December 31, 2022 and $9,634,000, or 87.4% of net service revenues, for the same period a year ago. The increase in gross profit in dollars and as a percentage of net sales on equipment sales and service revenues was was primarily the result of the increase in revenues of each as described above as well as increased availability and lower costs of components and transportation as compared to the same period last year which resulted from improvements within the Company’s supply chain. The increase in revenues resulted in improved overhead absorption rates. In addition, the increase in gross margin on service revenues was due, in part, to increased service revenues relating to the Company’s fire radios, which have higher monthly selling prices than the Company’s intrusion radios.
The Company's gross profit increased by $12,730,000 to $37,629,000, or 46.0% of net sales, for the six months ended December 31, 2022 as compared to $24,899,000, or 38.6% of net sales, for the same period a year ago. Gross profit on equipment sales was $12,269,000, or 23.1% of net equipment sales, for the six months ended December 31, 2022 and $6,464,000, or 15.0% of net equipment sales, for the same period a year ago. Gross profit on service revenues was $25,360,000, or 88.4% of net service revenues, for the six months ended December 31, 2022 and $18,435,000, or 86.7% of net service revenues, for the same period a year ago. The increase in gross profit in dollars and as a percentage of net sales on equipment sales and service revenues was was primarily the result of the increase in revenues of each as described above as well as increased availability and lower costs of components and transportation as compared to the same period last year which resulted from improvements within the Company’s supply chain. The increase in revenues resulted in improved overhead absorption rates. In addition, the increase in gross margin on service revenues was due, in part, to increased service revenues relating to the Company’s fire radios, which have higher monthly selling prices than the Company’s intrusion radios.
Research and development expenses for the three months ended December 31, 2022 increased $244,000 to $2,222,000, or 5.3% of net sales, as compared to $1,978,000, or 5.9% of net sales, for the same period a year ago. Research and development expenses for the six months ended December 31, 2022 increased $741,000 to $4,650,000, or 5.7% of net sales, as compared to $3,909,000, or 6.1% of net sales, for the same period a year ago. The increase in dollars was due primarily to salary increases and additional staff.
Selling, general and administrative expenses for the three months ended December 31, 2022 decreased by $391,000 or 4.8% to $7,804,000 from $8,195,000 for the same period a year ago. Selling, general and administrative expenses as a percentage of net sales decreased to 18.4% for the three months ended December 31 2022 as compared to 24.5% for the same period a year ago. The decrease in dollars resulted primarily from higher stock option expense and legal expenses incurred in the three months ended December 31, 2021. The decrease as a percentage of net sales was due primarily to the increase in net sales as partially offset by the aforementioned increase in expense dollars. Selling, general and administrative expenses for the six months ended December 31, 2022 increased by 753,000 or 4.8% to $16,294,000 from $15,541,000 for the same period a year ago. Selling, general and administrative expenses as a percentage of net sales decreased to 19.9% for the six months ended December 31 2022 as compared to 24.1% for the same period a year ago. The increase in dollars resulted primarily from increases in credit card processing fees, insurance expense and commission expenses. The decrease as a percentage of net sales was due primarily to the increase in net sales as partially offset by the aforementioned increase in expense dollars.
Interest and other income (expense), net for the three months ended December 31, 2022 increased by $129,000 to income of $187,000 as compared to income of $58,000 for the same period a year ago. Interest and other income (expense), net for the six months ended December 31, 2022 increased by $9,000 to income of $84,000 as compared to income of $75,000 for the same period a year ago.
Gain on extinguishment of debt resulted from a one-time gain in the three months ended September 30, 2021 which resulted from the forgiveness of the Company’s PPP loans as described in Note 8 to the condensed consolidated financial statements.